For PMS General Knowledge - Page 3

Shaa-Baaz · #21 Wednesday, February 18, 2009

Women Politcal Leaders

Angola -------- Queen Nzingha 1582-1663
Argentina ----- President Cristina Fernandez de Kirchner 2007–Present
Argentina ----- President Isabel Perón 1974–1976

Bahamas ---- Governor-General Dame Ivy Dumont 2001–2005
Bangladesh ---- Prime Minister Khaleda Zia 1991–1996, 2001–2006
Bangladesh ---- Prime Minister Sheikh Hasina Wajed 1996–2001
Barbados ---- Governor-general Dame Nita Barrow 1990–1995
Belize ---- Governor-general Dame Minita Gordon 1981–1993
Bermuda ---- Premier Pamela Gordon 1997–1998
Bermuda ---- Premier Jennifer Smith 1998–2003
Bolivia ---- Prime Minister Lidia Gueiler 1979–1980
Brazil ---- Queen Maria I 1815–1816
Brazil ---- Empress Isabel (regent) 1871–1872, 1876–1877, 1887–1888
Burundi ---- Prime Minister Sylvie Kinigi 1993–1994
Byzantium ---- (Roman Empire) Empress Theodora 1055–1056

Cambodia ---- Queen Ang Mey 1835–1840, 1844–1845
Cambodia ---- Queen Kossamak (joint ruler) 1955–1960
Canada ---- Governor-general Jeanne Sauvé 1984–1990
Canada ---- Prime Minister Kim Campbell 1993 (4 months)
Canada ---- Governor-general Adrienne Clarkson 1999–2005
Canada ---- Governor-general Michaëlle Jean 2005–
Central African Republic ---- Prime Minister Elizabeth Domitien 1974–1976
Cherokee Nation ---- Wilma Mankiller 1985–1995
Chile ---- President Michelle Bachelet 2006–
China ---- Empress Wu Chao 655–705
China ---- Dowager Empress Tsu-Hsi 1861–1908
China ---- Dowager Empress Longyu 1911–1912

Denmark ---- Queen Margaret I 1387–1412
Denmark ---- Queen Margrethe II 1972–present
Dominica ---- Prime Minister Mary Eugenia Charles 1980–1995

Easter Island Paramount ---- Chief Koreto Puakurunga 1868–1869?
Easter Island Paramount ---- Chief Carolina 1869?–1888?
Egypt ---- Queen Hatshepsut 1501–1498 B.C.
Egypt ---- Queen Tiye 1415–1340 B.C.
Egypt ---- Queen Nefertiti 1372–1350 B.C.
Egypt ---- Queen Nefertari 1292–1225 B.C.
Egypt ---- Queen Arsinoe II (joint ruler) 279–270 B.C.
Egypt ---- Queen Berenice 81–80 B.C.
Egypt ---- Queen Cleopatra VII 51–30 B.C.
Egypt ---- Empress Zauditu 1916–1930
Ethiopia ---- Empress Candace 332 B.C.
Ethiopia ---- Empress Zaudita 1916–1930

Faeroe Islands ---- Prime Minister Marita Petersen 1993–1994
Finland ---- President Tarja Halonen 2000–present
Finland ---- Prime Minister Anneli Jäätteenmäki 2003 (2 months)
France ---- Prime Minister Edith Cresson 1991–1992

Georgia ---- Queen Tamara 1184–1212
Germany ---- Chancellor Angela Merkel 2005–
Ghana ---- Queen Mother Yaa Asantewa 1863-1923
Great Britain ---- Boadicea, Queen of the Iceni c. 26–61
Great Britain ---- Queen Jane (Lady Jane Grey) 1553 (9 days)
Great Britain ---- Queen Mary I 1553–1558
Great Britain ---- Queen Elizabeth I 1558–1603
Great Britain ---- Queen Mary II (joint ruler) 1689–1702
Great Britain ---- Queen Anne 1702–1714
Great Britain ---- Queen Victoria 1837–1901
Great Britain ---- Queen Elizabeth II 1952–present
Great Britain ---- Prime Minister Margaret Thatcher 1979–1990
Grenada ---- Governor Dame Hilda Louisa Bynoe 1967–1972
Guyana ---- Prime Minister Janet Jagan 1997
Guyana ---- President Janet Jagan 1997–1999

Haiti ---- Provisional President Ertha Pascal-Trouillot 1990, 1991
Haiti ---- Prime Minister Claudette Werleigh 1995–1996
Hawaii ---- Queen Liliuokalani 1891–1893
Hungary ---- Queen Mary 1382–1387
Hungary ---- Queen Elizabeth 1439–1440
Hungary ---- Queen Maria Theresa 1740–1780

Iceland -----President Vigdis Finnbogadóttir 1980–1996
India --------Prime Minister Indira Gandhi 1966–1977, 1980–1984
Indonesia ---------President Megawati Sukarnoputri 2001–2004
Ireland ---------President Mary Robinson 1990–1997
Ireland -------President Mary McAleese 1997–present
Israel and Judah -----------Queen Athaliah 842–837 B.C.
Israel---------- Prime Minister Golda Meir 1969–1974
Italy ----------Queen Theodelinda 590
Italy ----------Queen Joanna I of Naples 1343–1381
Italy -------Queen Maria of Sicily 1377–1402
Italy ---------Queen Joanna II of Naples 1414–1435

Jamaica ---------Prime Minister Portia Simpson Miller 2006–
Japan ----------Empress Suiko Tenno 593–628
Japan ----------Empress Kogyoku 642–645
Japan ---------Empress Jito 686–697
Japan--------- Empress Gemmyo 703–724
Japan -Empress Koken (abdicated) 749–758
Japan -----Empress Shotuku-Koken 764–770
Japan -----Empress Toshi-ko 1762–1771

Latvia ------President Vaira Vike-Freiberga 1999–present
Lesser Armenia ---- Queen Zabel 1219–1226
Lesotho Paramount ------------Chief 'Mantsebo Amelia 'Matsaba Sempe 1941–1960
Liberia ---President Ellen Johnson-Sirleaf 2006–
Lithuania ---------Prime Minister Kazimiera Prunskiene 1990–1991
Luxembourg ---------Grand Duchess Marie Anne de Bragance (regent) 1908–1912
Luxembourg -------Grand Duchess Marie-Adélaïde 1912–1919
Luxembourg -------Grand Duchess Charlotte 1919–1964

Madagascar ----------Queen Ranavalona I 1828–1861
Madagascar ---Queen Rasoaherina 1863–1868
Madagascar ---Queen Ranavalona II 1868–1883
Madagascar -----Queen Ranavalona III (deposed) 1883–1897
Maldives -------Sultan Amina Rani Kilagefanu 1757–1759
Malta -----------President Agatha Barbara 1982–1987
Micronesia------ High Commissioner of Trust Territory of the Pacific Islands Janet J. McCoy 1981–1986
Monaco------ Princess Louise-Hippolyte 1731

Netherlands ------Queen Wilhelmina (abdicated) 1890–1948
Netherlands ------Queen Juliana 1948–1980
Netherlands ----Queen Beatrix 1980–present
Netherlands Antilles ---Prime Minister Lucinda da Costa Gomez-Matheeuws 1977
Netherlands Antilles ---Prime Minister Maria Liberia-Peters 1984–1986, 1988–1993
Netherlands Antilles ---Prime Minister Susanne Camelia-Romer 1993, 1998–1999
Netherlands Antilles ---Prime Minister Mirna Louisa-Godett 2003–2004
New Caledonia ----------President Marie-Noëlle Thémereau 2004–present
New Zealand -------Governor-general Dame Catherine Tizard 1990–1996
New Zealand ------Governor-general Dame Silvia Cartwright 2001–2006
New Zealand -------Prime Minister Jenny Shipley 1997–1999
New Zealand ----Prime Minister Helen Clark 1999–present
New Zealand -----(Maori community) Queen Te Ata-i Rangi-Kahu Koroki Te Rata Mahuta Tawhiao Potatau Te Wherowhero 1966–2006
Nicaragua------- President Violeta Barriosde Chamorro 1990–1997
Nigeria ---------Queen Amina of Zaria 1588-1589
Norway ------Queen Margaret 1387–1412
Norway -----Prime Minister Gro Harlem Brundtlandt 1981, 1986–1989, 1990–1996

Pakistan--- Prime Minister Benazir Bhutto 1988–1990, 1993–1996
Panama --------President Mireya Moscoso 1999–2004
Peru Prime--- Minister Beatriz Merino 2003 (6 months)
Philippines --------President Maria Corazon Aquino 1986–1992
Philippines ------President Gloria Macapagal-Arroyo 2001–present
Poland --------Queen Hedwige 1384–1399
Poland --------Premier Hanna Suchocka 1992–1993
Portugal -------Queen Maria I 1777–1816
Portugal --------Queen Maria II 1826–1828, 1834–1853
Portugal -----Prime Minister Maria de Lourdes Pintasilgo 1979 (149 days)

Roman Empire--Empress Irene 797–802
Russia --------Empress Catherine I 1725–1727
Russia ------Empress Anna Ivanovna 1730–1740
Russia ---------Empress Elizabeth Petrovna 1741–1762
Russia ----------Empress Catherine II (The Great) 1762–1796
Rwanda --------Prime Minister Agathe Uwilingiyimana 1993–1994

St. Lucia -----Governor-General Dame Pearlette Louisy 1997–present
São Tomé and Príncipe ----Prime Minister Maria das Neves 2002–2004
São Tomé and Príncipe ---Prime Minister Maria do Carmo Silveira 2005–present
Scotland-------------- Queen Mary Stuart (executed) 1542–1567
Seminole--------- Nation Betty Mae Jumper 1960–1969
Senegal ---------Mame Madior Boye 2001–2002
Sheba -----Queen Makeda 960 B.C.
Spain -------Queen Dona Urraca 1109–1126
Spain ---------Queen Juana I 1274–1307
Spain ----------Queen Juana II 1328–1349
Spain ----------Queen Dona Blanca 1425–1441
Spain ------Queen Isabella I (joint ruler) 1474–1504
Spain --------Queen Catalina de Albret 1481–1512
Spain ------Queen Isabella II 1833–1868
Sri Lanka --------Queen Anula 47–42 B.C.
Sri Lanka------- Queen Sivali 35 B.C.
Sri Lanka-------- Queen Lilavati 1197–1200, 1209–1212
Sri Lanka ------------Queen Kalyanavati 1202–1208
Sri Lanka -----Prime Minister Sirimavo Bandaranaike 1960–1965, 1970–1977, 1994–2000
Sri Lanka ---------President Chandrika Kumaratunga 1994–2005
Sudan ------------Amanirenas, Queen of Cush late 1st century B.C.
Sweden ----------Queen Christina (abdicated) 1632–1654
Sweden ----------Queen Ulrica Eleonora (abdicated) 1718–1720
Switzerland -------President Ruth Dreifuss 1999

Tonga Chief --------Tupoumahe'ofo 17?–1793
Tonga Queen -------Salote Tubou III 1918–1965
Turkey Prime -------Minister Tansu Çiller 1993–1996
Ukraine Prime -------Minister Yulia Timoshenko 2005

Wallis Ruler -----Toifale 1825
Wallis Ruler -----Falakika Seilala Lavelua 1858–1869
Wallis Ruler -----Amelia Tokagahahau Aliki Lavelua 1869–1895
Wallis Ruler -----Aloisia Lavelua 1953–1958
Yugoslavia -----Premier Milka Planinc 1982–1986
Zululand -------Queen Nandi 1778–1826

Shaa-Baaz · #22 Wednesday, February 18, 2009

Forms of Government

1)Aristocracy:
Govt by noble people.

2)Autocracy:
Govt by one person.

3)Authoritarian: E
xtremely powerful Govt.

4)Bureaucracy:
Govt that is carried on through officers.

5)Caliphate:
Govt that is carried on through a caliph.

6)Democracy:
Govt of the people, by the people, for the people.

7)Dictatorship:
Govt by one dictator.

8)Depotic:
Govt by the tyrant.

9)Monarchy:
Govt by a monarch.

10)Oligarchy:
Govt by small group.

11)Plutocracy:
Govt by rich people.

12)Theocracy:
Govt that is carried on through religious people.

13)Totalitarian:
A one party Govt.

Shaa-Baaz · #23 Friday, February 20, 2009

Speed of light in different units

299,792,458 -------meter/second
1,079,252,848.8--- kilometers/hour
670,616,629-------miles/hour
186,282-----------miles/second

Length of time for light to travel..

One foot --- 1.0 nanosecond
One meter --- 3.3 nanoseconds
One km---- 3.3 microseconds
One mile--- 5.4 microseconds
Around Earth's equator--- -----------------------0.13 seconds
From Earth to geostationary orbit and back---- 0.24 seconds
From Earth to the moon ----------------------- 1.3 seconds
From Earth to the sun------------ 8.3 minutes
To Earth from Alpha Centauri - 4.4 years
From edge to edge of the Milky Way ----------- 100,000 years

1 Second = 1000000000 Nanoseconds

1 Second = 1000000 microseconds

-------------------------------------------------------------

Speed Of Sound

761.6- miles per hour
330 ---meters per second
1225 --kilometers per hour

Shaa-Baaz · #24 Friday, February 20, 2009

Human Body

1. What is the body temperature of a normal man?

A. 81.1oC
B. 36.9oC
C. 98.6oC
D. 21.7oC

2. Which of the following helps in clotting of blood?

A. Vitamin B1
B. Vitamin B2
C. Vitamin D
D. Vitamin K

3. Total volume of blood in a normal adult human being is

A. 5-6 liters
B. 3-4 liters
C. 8-10 liters
D. 10-12 liters

4. Red blood corpuscles are formed in the

A. Liver
B. Bone marrow
C. Kidneys
D. Heart

5. How many bones are there in an adult human being?

A. 210
B. 260
C. 206
D. 300

6. The pancreas secretes

A. Insulin
B. Bile juice
C. Peptic juice
D. None of these

7. Tibia is a bone found in the

A. Skull
B. Arm
C. Leg
D. Face

8. The largest part of the human brain is the

A. Medulla oblongata
B. Cerebellum
C. Cerebrum
D. None of these

9. What is the main component of bones and teeth?

A. Calcium carbonate
B. Calcium phosphate
C. Calcium sulphate
D. Calcium nitrate

10. The main constituent of hemoglobin is

A. Chlorine
B. Iron
C. Calcium
D. None of these

11. The main function of the kidney is

A. To control blood pressure
B. To control body temperature
C. To remove waste product from the body
D. To help in digestion of food

12. The function of hemoglobin is

A. Transportation of oxygen
B. Destruction of bacteria
C. Prevention of anemia
D. Utilization of energy

13. Which of the following glands secrete tears?

A. Lachrymal
B. Pituitary
C. Thyroid
D. Pancreas

14. Which is the largest gland in the human body?

A. Thyroid
B. Liver
C. Pancreas
D. None of these

15. Which is the largest organ in the human body?

A. Liver
B. Heart
C. Skin
D. Kidney

16. A person of which of the following blood groups is called a universal donor?
A. O
B. AB
C. A
D. B

17. Which gland in the human body is called the master gland?
A. Pancreas
B. Thyroid
C. Pituitary
D. Spleen

18. How many bones are there in a newly born infant?

A. 206
B. 230
C. 280
D. 300

19. Which of the following have maximum calorific value?
A. Carbohydrates
B. Fats
C. Proteins
D. Vitamins

20. Which of the following vitamins promote healthy functioning of eyes in human beings?
A. Vitamin B
B. Vitamin C
C. Vitamin A
D. Vitamin D

21. The average heartbeat per minute in a normal man is
A. 50
B. 70
C. 80
D. 100

22. A person with which of the following blood groups can receive blood of any group?
A. A
B. AB
C. B
D. O

23. Malaria is a disease which effects the
A. Heart
B. Lungs
C. Spleen
D. Kidneys

24. Which of the following diseases is caused by virus?
A. Small pox
B. Tuberculosis
C. Malaria
D. Cholera

25. Medulla oblongata is a part of human
A. Heart
B. Brain
C. Liver
D. Sex organ

26. Myopia is a disease connected with
A. Ears
B. Eyes
C. Lungs
D. Brain

27. Leukemia is a disease of the
A. Lungs
B. Blood
C. Skin
D. Nerves

28. Short-sightedness can be corrected by using
A. Convex lens
B. Concave lens
C. Convex-concave lens
D. Concave-convex lens

29. Trachoma is a disease of the
A. Liver
B. Eyes
C. Lungs
D. Kidneys

30. Match the following
Column I Column II

A. Beriberi 1. Vitamin A
B. Scurvy 2. Vitamin B
C. Rickets 3. Vitamin C
D. Night Blindness 4. Vitamin D

A B C D

(a) 3 2 1 4

(b) 2 1 3 4

(c) 2 3 4 1

(d) 2 3 1 4

31. Typhoid and cholera are typical examples of
A. Infectious diseases
B. Air-borne disease
C. Water-borne disease
D. None of these

32. Pyorrhea is a disease of the
A. Nose
B. Gums
C. Heart
D. Lungs

33. Lack of what causes diabetes.
A. Sugar
B. Insulin
C. Calcium
D. Vitamins

34. Appendix is appendix is a part of
A. Small intestine
B. Large intestine
C. Stomach
D. Liver

35. Match the following columns
Column I Column II

A. Cataract 1. Bones
B. Jaundice 2. Eyes
C. Diabetes 3. Liver
D. Arthritis 4. Pancreas

A B C D

(a) 2 3 4 1

(b) 2 3 1 4

(c) 1 3 4 2

(d) 3 2 4 1

36. Bronchitis is a disease of which of the following organs?
A. Blood
B. Bladder
C. Liver
D. Respiratory tract

37. ECG is used for the diagnosis of aliments of
A. Brain
B. Heart
C. Kidneys
D. Lungs

38. Biopsy is done on
A. Tissues taken from a dead body
B. Tissues taken form a living body
C. Blood from veins
D. Blood from arteries

39. Barium is used for
A. Checking blood group
B. X-ray of alimentary canal
C. X-ray of brain
D. None of these

40. Dialysis is used for the treatment of
A. Kidney failure
B. Heart weakness
C. Brain diseases
D. None of these

41. Insulin is injected into the intestines by
A. Pancreas
B. Liver
C. Stomach
D. Gall bladder

42. Lock Jaw, i.e., difficulty in opening the mouth is a symptom of
A. Cholera
B. Plague
C. Tetanus
D. Diphtheria

43. Which of the following pairs is incorrect?
A. Plague-rats
B. Rabies-dog
C. Tapeworm-pig
D. Poliomyelitis-monkey

44. Match the following columns
Column I Column II

A. Air-borne 1. Tetanus
B. Water-borne 2. Tuberculosis
C. Contact 3. Cholera
D. Wound 4. Syphilis

A B C D

(a) 2 3 1 4

(b) 2 3 4 1

(c) 3 2 4 1

(d) 4 3 2 1

45. Ricketts is a disease of the
A. Bones
B. Tissue
C. Muscles
D. Blood

46. Which of the following statements is correct
A. Pulmonary artery carries pure blood
B. Pulmonary artery carries impure blood
C. Pulmonary vein carries impure blood
D. None of these

47. Lungs are situated in the
A. Abdominal cavity
B. Pericardial cavity
C. Buccal cavity
D. Thoracic cavity

48. The human cell contains
A. 44 chromosomes
B. 48 chromosomes
C. 46 chromosomes
D. 23 chromosomes

49. Enzymes help in
A. Respiration
B. Digestion of food
C. Immune system
D. Reproduction

50. Food is normally digested in the
A. Liver
B. Stomach
C. Small intestines
D. Large intestines

Answers

1. b 2. d 3. a 4. b 5. c
6. a 7. c 8. c 9. b 10. b
11. c 12. a 13. a 14. b 15. c
16. a 17. c 18. d 19. a 20. c
21. b 22. b 23. c 24. a 25. b
26. b 27. b 28. b 29. b 30. c
31. c 32. b 33. b 34. b 35. a
36. d 37. b 38. b 39. b 40. a
41. a 42. c 43. d 44. b 45. a
46. b 47. d 48. c 49. b 50. c

Emotions · #25 Friday, February 20, 2009

Advisory Committee on Administrative and Budgetary Questions - New York (ACABQ)
Consultative Committee on Programme and Operational Questions - Geneva, Switzerland (CCPOQ)
Economic Commission for Europe - Geneva, Switzerland (ECE)
Food and Agriculture Organization of the United Nations - Rome, Italy (FAO)
Information Systems Coordination Committee - Geneva, Switzerland (ISCC)
Inter-agency Committee on Sustainable Development - New York, USA (IACSD)
International Atomic Energy Agency - Vienna, Austria (IAEA)
International Bureau of Education - Geneva, Switzerland (IBE)
International Centre for Science and High Technology - Trieste, Italy (ICS)
International Civil Aviation Organization - Montreal, Canada (ICAO)
International Civil Service Commission - New York, USA (ICSC)
International Computing Centre - Geneva, Switzerland (ICC)
International Court of Justice - The Hague, The Netherlands (ICJ)
International Fund for Agricultural Development - Rome, Italy (IFAD)
International Institute on Ageing - Valetta, Malta (INIA)
International Labour Organization - Geneva, Switzerland (ILO)
International Monetary Fund - Washington, USA (IMF)
International Research and Training Institute for the Advancement of Women - Santo Domingo, Dominican Republic (INSTRAW)
International Telecommunication Union - Geneva, Switzerland (ITU)
International Trade Centre UNCTAD/WTO - Geneva, Switzerland (ITC)
International Training Centre of the ILO - Turin, Italy (ILO/ITC)
Joint Inspection Unit - Geneva, Switzerland (JIU)
Joint Inter-agency Meeting on Computer-assisted Translation and Terminology - Geneva, Switzerland (JIAMCATT)
Joint United Nations Information Committee - New York, USA (JUNIC)
Joint United Nations Programme on HIV/AIDS - Geneva, Switzerland (UNAIDS)
Multilateral Investment Guarantee Agency - Washington, USA (MIGA)
Organizational Committee of ACC - New York, USA (OC)
Outer Space Affairs, Office for - Vienna, Austria (OOSA)
United Nations Board of Auditors - New York, USA
United Nations Centre for Human Settlements (Habitat) - Nairobi, Kenya (UNCHS (Habitat))
United Nations Children's Fund - New York, USA (UNICEF)
United Nations Commission on International Trade Law - Vienna, Austria (UNCITRAL)
United Nations Common Supply Database - Oslo, Norway (UNCSD)
United Nations Convention to Combat Desertification - Bonn, Germany (UNCCD)
United Nations Conference on Trade and Development - Geneva, Switzerland (UNCTAD)
United Nations Development Fund for Women - New York, USA (UNIFEM)
United Nations Development Programme - New York, USA (UNDP)
United Nations Educational, Scientific and Cultural Organization - Paris, France (UNESCO)
United Nations Environment Programme - Nairobi, Kenya (UNEP)
United Nations Framework Convention on Climate Change - Bonn, Germany (UNFCCC)
United Nations Headquarters - New York, USA (UN)
United Nations High Commissioner for Human Rights, Office of the - Geneva, Switzerland (UNHCHR)
United Nations High Commissioner for Refugees, Office of the - Geneva, Switzerland (UNHCR)
United Nations Industrial Development Organization - Vienna, Austria (UNIDO)
United Nations Institute for Disarmament Research - Geneva, Switzerland (UNIDIR)
United Nations Institute for Training and Research - Geneva, Switzerland (UNITAR)
United Nations International Drug Control Programme - Vienna, Austria (UNDCP)
United Nations International School -New York, USA (UNIS)
United Nations Interregional Crime and Justice Research Institute - Rome, Italy (UNICRI)
United Nations Joint Staff Pension Fund - New York, USA (UNJSPF)
United Nations Office at Geneva - Geneva, Switzerland (UNOG)
United Nations Office at Vienna - Vienna, Austria (UNOV)
United Nations Special Coordinator in the Occupied Territories - Gaza (UNSCO)
United Nations Population Fund - New York, USA (UNFPA)
United Nations Postal Administration - Vienna, Austria (UNPA)
United Nations Research Institute for Social Development - Geneva, Switzerland (UNRISD)
United Nations Staff College - Turin, Italy (UNSC)
United Nations University - Tokyo, Japan (UNU)
United Nations Volunteers - Bonn, Germany (UNV)
World Bank - Washington, USA (IBRD)
World Food Programme - Rome, Italy (WFP)
World Health Organization - Geneva, Switzerland (WHO)
World Intellectual Property Organization - Geneva, Switzerland (WIPO)
World Meteorological Organization - Geneva, Switzerland (WMO)
World Tourism Organization - Madrid, Spain
World Trade Organization - Geneva Switzerland (WTO)

Shaa-Baaz · #26 Monday, February 23, 2009

Alloys

Gun Metal
Copper 90%, Tin 10%

Steel
Iron 99 % , Carbon 1%

Stainless Steel
Iron with 0.1-2.1% carbon upto 27% chromium or 20% tunsten or 15% Nickal

Petwar
Tin,Antimony & Copper

Bronze
Copper, Tin and Zinc

German Silver
Copper,Zinc and Nickel

Electrum
Gold & Silver

18 carat Gold
Gold 75%, Silver & copper 25%

Dentist Amalgam
70% Mercury 30% Copper

Yellow Brass
Copper 67% Zinc 33%

Spiegeleisen
Iron , 15% manganese and carbon and silicon

Brass
Copper & 38% Zinc

Nichrome
Nickel & Chromium

Plumbers Solder
Lead and tin

Mu Metal
77% nickel, 15% iron, plus copper and molybdenum

An amalgam
refers to alloys of mercury.

Shaa-Baaz · #27 Sunday, March 01, 2009

1. Question: A man with a load jumps from a high building. What will be the load experienced by him?

Answer: Zero, because while falling, both the man and the load are falling at the same acceleration i.e. acceleration due to gravity.

2. Question: A piece of chalk when immersed in water emits bubbles. Why?

Answer: Chalk consists of pores forming capillaries. When it is immersed in water, the water begins to rise in the capillaries and air present there is expelled in the form of bubbles.

3. Question: Why does a liquid remain hot or cold for a long time inside a thermos flask?

Answer: The presence of air, a poor conductor of heat, between the double glass wall of a thermos flask, keeps the liquid hot or cold inside a flask for a long time.

4. Question: Why does a ball bounce upon falling?

Answer: When a ball falls, it is temporarily deformed. Because of elasticity, the ball tends to regain its original shape for which it presses the ground and bounces up (Newton's Third Law of Motion).

5 Question: Why is standing in boats or double decker buses not allowed, particularly in the upper deck of buses?

Answer: On tilting the centre of gravity of the boat or bus is lowered and it is likely to overturn.

6. Question: Why is it recommended to add salt to water while boiling dal?

Answer: By addition of salt, the boiled point of water gets raised which helps in cooking the dal sooner.

7. Question: Why is it the boiling point of sea water more than that of pure water?

Answer: Sea water contains salt, and other impurities which cause an elevation in its boiling point.

8. Question: Why is it easier to spray water to which soap is added?

Answer: Addition of soap decreases the surface tension of water. The energy for spraying is directly proportional to surface tension.

9. Question: Which is more elastic, rubber or steel?

Answer: Steel is more elastic for the same stress produced compared with rubber.

10. Question: Why is the sky blue?

Answer: Violet and blue light have short waves which are scattered more than red light waves. While red light goes almost straight through the atmosphere, blue and violet light are scattered by particles in the atmosphere. Thus, we see a blue sky.

11. Question: Why Does ink leak out of partially filled pen when taken to a higher altitude?

Answer: As we go up, the pressure and density of air goes on decreasing. A Partially filled pen leaks when taken to a higher altitude because the pressure of air acting on the ink inside the tube of the pen is greater than the pressure of the air outside.

12. Question: On the moon, will the weight of a man be less or more than his weight on the earth?

Answer: The gravity of the moon is one-sixth that of the earth; hence the weight of a person on the surface of the moon will be one-sixth of his actual weight on earth.

13. Question: Why do some liquid burn while others do not?

Answer: A liquid burns if its molecules can combine with oxygen in the air with the production of heat. Hence, oil burns but water does not.

14. Question: Why can we see ourselves in a mirror?

Answer: We see objects when light rays from them reach our eyes. As mirrors have a shiny surface, the light rays are reflected back to us and enter our eyes.

15. Question: Why does a solid chunk of iron sink in water but float in mercury?

Answer: Because the density of iron is more than that of water bus less than that of mercury.

16. Question: Why is cooking quicker in a pressure cooker?

Answer: As the pressure inside the cooker increases, the boiling point of water is raised, hence, the cooking process is quicker.

17. Question: When wood burns it crackles. Explain?

Answer: Wood contains a complex mixture of gases and tar forming vapors trapped under its surface. These gases and tar vapors escape, making a cracking sound.

18. Question: Why do stars twinkle?

Answer: The light from a star reaches us after refraction as it passes through various layers of air. When the light passes through the earth?s atmosphere, it is made to flicker by the hot and cold ripples of air and it appears as if the stars are twinkling.

19. Question: Why is it easier to roll a barrel than to pull it?

Answer: Because the rolling force of friction is less than the dynamic force of sliding friction.

20. Question: If a feather, a wooden ball and a steel ball fall simultaneously in a vacuum, which one of these would fall faster?

Answer: All will fall at the same speed in vacuum because there will be no air resistance and the earth?s gravity will exert a similar gravitational pull on all.

21. Question: When a man fires a gun, he is pushed back slightly. Why?

Answer: As the bullet leaves the nozzle of the gun?s barrel with momentum in a forward direction, as per Newton's Third Law of Motion, the ejection imparts to the gun as equal momentum in a backward direction.

22. Question: Ice wrapped in a blanket or saw dust does not melt quickly. Why?

Answer: Both wood and wool are bad conductors of heat. They do not permit heat rays to reach the ice easily.

23. Question: Why do we perspire on a hot day?

Answer: When the body temperature rises, the sweat glands are stimulated to secrete perspiration. It is nature's way to keep the body cool. During the process of evaporation of sweat, body heat is taken away, thus giving a sense of coolness.

24. Question: Why does ice float on water but sink in alcohol?

Answer: Because ice is lighter than water it floats on it. However, ice is heavier than alcohol and therefore it sinks in alcohol.

25. Question: Why do we perspire before rains?

Answer: Before the rain falls, the atmosphere gets saturated with water vapors; as a result, the process of evaporation of sweat is delayed.

26. Question: Why does a thermometer kept in boiling water show no change in reading after 1000C?

Answer: The boiling point of water is 1000C. Once water starts boiling at this temperature, thermometer records no change in temperature. The quantity of heat supplied is being utilized as latent heat of evaporation to convert the water at boiling point into vapour.

27. Question: Why do we bring our hands close to the mouth while shouting across to someone far away?

Answer: By keeping hands close to mouth the sound is not allowed to spread (Phenomenon of diffraction of sound) in all direction, but is directed to a particular direction and becomes louder.

28. Question: Why does a corked bottle filled with water burst if left out on a frosty night?

Answer: Because of low temperature the water inside the bottle freezes. On freezing it expands, thereby its volume increases and pressure is exerted on the walls.

29. Question: Why is a small gap left at the joint between two rails?

Answer: To permit expansion of rails due to heat generated by friction of a moving train.

30. Question: Why cannot a copper wire be used to make elements in electric heater?

Answer: Copper melts at 108.30C and forms a black powder on reacting with atmospheric oxygen. For heater elements a metal should have more resistance to produce heat.

31. Question: Why are water or mercury droplets always round when dropped on a clean glass?

Answer: The surface of a liquid is the seat of a special force as a result of which molecules on the surface are bound together to form something like a stretched membrane. They tend to compress the molecules below to the smallest possible volume, which causes the drop to take a round shape as for a given mass he sphere has minimum volume.

32. Question: Why does a balloon filled with hydrogen rise in the air?

Answer: Weight of hydrogen is less than the weight of air displaced by it. In balloons hydrogen is normally filled because it is lighter than air.

33. Question: Why do we lean forward while climbing a hill?

Answer: In order to keeps the vertical line passing through our centre of gravity always between our feet, which is essential to attain equilibrium or stability.

34. Question: Why does smoke curl up in the air?

Answer: Smoke contains hot gases which being lighter in weight, follows a curved path because of the eddy currents that are set up in the air.

35. Question: Why does an electric bulb explode when it is broken?

Answer: The bulb encompasses partial vacuum and as it breaks, air rushes in causing a small explosion.

36. Question: Why does a man fall forward when he jumps out of a running train or bus?

Answer: He is in motion while in the train or bus. When he jumps out, his feet comes to rest while touching the ground but his upper portion which is still in motion propels him forward.

37. Question: Why does an ordinary glass tumbler crack when very hot tea or milk is poured in it?

Answer: When a hot liquid is poured into a tumbler, the inner layer of the tumbler gets heated, it expands before the outer layer and an unequal expansion of both layers causes the tumbler to crack.

38. Question: Why is a compass used as an indicator of direction?

Answer: The magnetic needles of a compass under the influence f the earth?s magnetic field lie in a north-south direction. Hence, we can identify direction.

39. Question: Why is water from a hand pump warm in winter and cold in summer?

Answer: In winter, the outside temperature is lower than that of water flowing out of the pump, and therefore, the water is warm. Whereas in summer, the outside temperature is higher than the water of the pump, and therefore, it feels cold.

40. Question: Why is a rainbow seen after a shower?

Answer: After a shower, the clouds containing water droplets act like a prism through which the white light is dispersed producing a spectrum.

41. Question: Why does a swimming pool appear less deep than is actually is?

Answer: The rays of light coming from the bottom of the pool pass from a denser medium (water) to a rarer medium (air) and are refracted (bend away from the normal). When the rays return to the surface, they form an image of the bottom of the pool at a point, which is little above the real position.

42. Question: Why is one?s breath visible in winter but not in summer?

Answer: In winter, water vapor contained in the breath condenses into small droplets, which become visible but in summer they are quickly evaporated and not seen.

43. Question: Why doesn?t the electric filament in an electric bulb burn up?

Answer: Firstly, because is made of tungsten which has a very high melting point (34100C) whereas the temperature of the filament required to glow is only 2700oC. Secondly, oxygen is absent since the bulb is filled with an inert gas which does not help in burning.

44. Question: Why does blotting paper absorb ink?

Answer: Blotting paper has fine pores, which act like capillaries. When a portion of blotting paper is brought in contact with ink, ink enters the pores due to surface tension (capillary action f liquids) and is absorbed.

45. Question: Why does a small iron sink in water but a large ship float?

Answer: The weight of water displaced by an iron ball is less than its own weight, whereas water displaced by the immersed portion of a ship is equal to its weight (Archimedes? Principle).

46. Question: Why does ice float on water?

Answer: The weight of the ice block is equal to the weight of the liquid displaced by the immersed portion of the ice.

47. Question: Why does moisture gather outside a tumbler containing cold water?

Answer: The water vapour in the air condenses on cooling and appears as droplets of water.

48. Question: Why does kerosene float on water?

Answer: Because the density of kerosene is less than that of water. For the same reason cream rises in milk and floats at the top.

49. Question: Why is the water in an open pond cool even on a hot summer day?

Answer: As the water evaporates from the open surface of a pond, heat is taken away in the process, leaving the surface cool.

50. Question: Why is it less difficult to cook rice or potatoes at higher altitudes?

Answer: Atmospheric pressure at higher altitudes is low and boils water below 100C. The boiling point of water is directly proportional to the pressure on its surface.

51. Question: Why is it difficult to breathe at higher altitudes?

Answer: Because of low air pressure at higher altitudes the quantity of air is less, and so that of oxygen.

52. Question: Why are winter nights and summer nights warmer during cloudy weather than when the sky is clear?

Answer: Clouds being bad conductors of heat do not permit radiation of heat from land to escape into the sky. As this heat remains in the atmosphere, the cloudy nights are warmer.

53. Question: Why is a metal tyre heated before it is fixed on wooden wheels?

Answer: On heating, the metal tyre expands by which its circumference also increases. This makes fixing the wheel easier and therefore cooling down shrinks it; thus fixing the tyre tightly.

54. Question: Why is it easier to swim in the sea than in a river?

Answer: The density of sea water is higher; hence the up thrust is more than that of river water.

55. Question: Who will possibly learn swimming faster-a fat person or a thin person?

Answer: The fat person displaces more water which will help him float much more freely compared to a thin person.

56. Question: Why is a flash of lightening seen before thunder?

Answer: Because light travels faster than sound, it reaches the earth before the sound of thunder.

57. Question: Why cannot a petrol fire be extinguished by water?

Answer: Water, which is heavier than petrol, slips down permitting the petrol to rise to the surface and continue to burn. Besides, the existing temperature is so high that the water poured on the fire evaporates even before it can extinguish the fire. The latter is true if a small quantity of water is poured.

58. Question: Why does water remain cold in an earthen pot?

Answer: There are pores in an earthen pot which allow water to percolate to the outer surface. Here evaporation of water takes place thereby producing a cooling effect.

59. Question: Why do we place a wet cloth on the forehead of a patient suffering from high temperature?

Answer: Because of body?s temperature, water evaporating from the wet cloth produces a cooling effect and brings the temperature down.

60. Question: When a needle is placed on a small piece of blotting paper which is place on the surface of clean water, the blotting paper sinks after a few minutes but the needle floats. However, in a soap solution the needle sinks. Why?

Answer: The surface tension of clean water being higher than that of a soap solution, it cans support the weight of a needle due to its surface tension. By addition of soap, the surface tension of water reduces, thereby resulting in the sinking of the needle.

61. Question: To prevent multiplication of mosquitoes, it is recommended to sprinkle oil in the ponds with stagnant water. Why?

Answer: Mosquitoes breed in stagnant water. The larvae of mosquitoes keep floating on the surface of water due to surface tension. However, when oil is sprinkled, the surface tension is lowered resulting in drowning and death of the larvae.

62. Question: Why does oil rise on a cloth tape of an oil lamp?

Answer: The pores in the cloth tape suck oil due to the capillary action of oil.

63. Question: Why are ventilators in a room always made near the roof?

Answer: The hot air being lighter in weight tends to rise above and escape from the ventilators at the top. This allows the cool air to come in the room to take its place.

64. Question: How does ink get filled in a fountain pen?

Answer: When the rubber tube of a fountain pen immersed in ink is pressed, the air inside the tube comes out and when the pressure is released the ink rushes in to fill the air space in the tube.

65. Question: Why are air coolers less effective during the rainy season?

Answer: During the rainy reason, the atmosphere air is saturated with moisture. Therefore, the process of evaporation of water from the moist pads of the cooler slows down thereby not cooling the air blown out from the cooler.

66. Question: Why does grass gather more dew in nights than metallic objects such as stones?

Answer: Grass being a good radiator enables water vapour in the air to condense on it. Moreover, grass gives out water constantly (transpiration) which appears in the form of dew because the air near grass is saturated with water vapour and slows evaporation. Dew is formed on objects which are good radiations and bad conductors.

67. Question: If a lighted paper is introduced in a jar of carbon dioxide, its flame extinguishes. Why?

Answer: Because carbon dioxide does not help in burning. For burning, oxygen is required.

68. Question: Why does the mass of an iron increase on rusting?

Answer: Because rust is hydrated ferric oxide which adds to the mass of the iron rod. The process of rusting involves addition of hydrogen and oxygen elements to iron.

69. Question: Why does milk curdle?

Answer: Lactose (milk sugar) content of milk undergoes fermentation and changes into lactic acid which on reacting with milk protein (casein) form curd.

70. Question: Why does hard water not lather soap profusely?

Answer: Hard water contains sulphates and chlorides of magnesium and calcium which forms an insoluble compound with soap. Therefore, soap does not lather with hard water.

71. Question: Why is it dangerous to have charcoal fire burning in a closed room?

Answer: When charcoal burns it produces carbon monoxide which is suffocating and can cause death.

72. Question: Why is it dangerous to sleep under trees at night?

Answer: Plants respire at night and give out carbon dioxide which reduces the oxygen content of air required for breathing.

73. Question: Why is a new quilt warmer than an old one?

Answer: In a new quilt the cotton is not compressed and as such it encloses more air which is bad conductor of heat. Therefore, it does not allow heat to pass.

74. Question: Curved rail tracks or curved roads are banked or raised on one side. Why?

Answer: Because a fast moving train or vehicle leans inwards while taking turn and the banked or raised track provides required centripetal force to enable it to move round the curve.

75. Question: How do bats fly in dark?

Answer: When bats fly they produce ultrasonic sound waves which are reflected back to them from the obstacles in their way and hence they can fly without difficulty.

76. Question: Water pipes often burst at hill stations on cold frosty nights. Why?

Answer: The temperature may fall below 00C during cold frosty nights which converts the water inside the pipes into ice, resulting in an increase in volume. This exerts great force on the pipes and as a result, they burst.

77. Question: Why are white clothes more comfortable in summer than dark or black ones?

Answer: White clothes are good reflectors and bad absorbers of heat, whereas dark or black clothes are good absorbers of heat. Therefore, white clothes are more comfortable because they do not absorb heat from the sun rays.

78. Question: Why does a rose appear red grass green in daylight?

Answer: Rose absorbs all the constituent colors of white light except red which is reflected to us. Similarly, grass absorbs all colors except green which is reflected t us.

79. Question: Why does a ship rise as it enters the sea from a river?

Answer: The density of sea water is high due to impurities and salts compared to river water as a result; the upthurst produced by the sea water on the ship is more than that of river water.

80. Question: Why are fuse provided in electric installations?

Answer: A safety fuse is made of a wire of metal having a very low melting point. When excess current flows in, the wire gets heated, melts and breaks the circuit. By breaking the circuit it saves electric equipment or installations from damage by excessive flow of current.

81. Question: Why is it easier to lift a heavy object under water than in air?

Answer: Because when a body is immersed in water, it experiences an upward thrust (Archimedes? Principle) and loses weight equal to the weight of the water displaced by its immersed potion, and hence, is easier to lift objects.

82. Question: If a highly pumped up bicycle tyre is left in the hot sunlight, it bursts. Why?

Answer: The air inside the tube increases in volume when heated up. As sufficient space for the expansion of the air is not available because the tube is already highly pumped, it may result in bursting of the tyre.

83. Question: What will be the color of green in blue light?

Answer: Grass will appear dark in color because it absorbs all other colors of the light except its own green color. The blue light falling on grass will be absorbed by it, and hence, it will appear dark in color.

84. Question: Why do two eyes give better vision than one?

Answer: Because two eyes do not form exactly similar images and he fusion of these two dissimilar images in the brain gives three dimensions of the stereoscopic vision

Shaa-Baaz · #28 Monday, March 02, 2009

1-The platypus and the echidna are the only mammals that:

A) Lay eggs
B) Have green blood
C) Live in Antarctica
D) Eat eucalyptus leaves

2-What is special about Sirius, the Dog Star?

A) It is the only star first observed by Albert Einstein
B) It is the brightest star in the sky
C) It always lies directly above the North Pole
D) It emits staccato barking sounds which radio telescopes can detect

3-An android is any robot that:

A) Has more than one basic function
B) Has the ability to make decisions and formulate plans
C) Is built by other robots
D) Looks and acts like a human

4-Charles Darwin began developing his theory of evolution while voyaging on a ship named:

A) The Enterprise
B) The Beagle
C) The Santa Maria
D) The Endeavour

5-Kinetic energy is:

A) Life energy, possessed only by living organisms
B) Only important at subatomic distances
C) Energy of movement
D) A rare form of energy sometimes observed in deep space

6-It is now believed that dinosaurs became extinct because of:

A) Viral diseases
B) Hunting by early humans
C) A worldwide period of climatic cooling
D) A meteorite impact

7-If you were to take a lump of coal and squeeze for a long time at very high temperatures, you would end up with:

A) Graphite
B) Volcanic glass, also known as obsidian
C) A smaller lump of coal
D) A diamond

8-Where should one go to find the “ablative absolute”?

A) A book of Latin grammar
B) A film by visionary German director Fritz Lang
C) An Irish monastery
D) A plastic surgeon

9-The metal mercury

A) Is the hardest known metal
B) Is a liquid at room temperature
C) Is highly radioactive
D) Is extensively used in aircraft construction

10-Unlike most other fish, sharks have no:

A) Bones
B) Teeth
C) Gills
D) Liver

11-The galaxy we live in is called the Milky Way. It is shaped approximately like:

A) A round ball
B) A doughnut
C) A pretzel
D) A flat spiral

answers

1-A
2-B
3-D
4-B
5-C
6-D
7-D
8-
9-B
10-A
11-D

Shaa-Baaz · #29 Tuesday, March 03, 2009

Layers of the Earth's Atmosphere

The atmosphere is divided into five layers. It is thickest near the surface and thins out with height until it eventually merges with space.

1) The troposphere is the first layer above the surface and contains half of the Earth's atmosphere. Weather occurs in this layer.
2) Many jet aircrafts fly in the stratosphere because it is very stable. Also, the ozone layer absorbs harmful rays from the Sun.
3) Meteors or rock fragments burn up in the mesosphere.
4) The thermosphere is a layer with auroras. It is also where the space shuttle orbits.
5) The atmosphere merges into space in the extremely thin exosphere. This is the upper limit of our atmosphere.
The troposphere is the lowest layer of the Earth's atmosphere. The air is very well mixed and the temperature decreases with altitude.

1-Troposphere

Air in the troposphere is heated from the ground up. The surface of the Earth absorbs energy and heats up faster than the air does. The heat is spread through the troposphere because the air is slightly unstable.
Weather occurs in the Earth's troposphere.

2-Stratosphere

The top of the stratosphere occurs at 50 km (31 miles) altitude.
Ozone, an unusual type of oxygen molecule that is relatively abundant in the stratosphere, heats this layer as it absorbs energy from incoming ultraviolet radiation from the Sun. Temperatures rise as one moves upward through the stratosphere. This is exactly the opposite of the behavior in the troposphere in which we live, where temperatures drop with increasing altitude

3-Mesosphere

The mesosphere starts at 50 km (31 miles) above Earth's surface and goes up to 85 km (53 miles) high.What do we know about the mesosphere? Most meteors from space burn up in this layer. A special type of clouds, called "noctilucent clouds", sometimes forms in the mesosphere near the North and South Poles. These clouds are strange because they form much, much higher up than any other type of cloud. There are also odd types of lightning in the mesosphere. These types of lightning, called "sprites" and "ELVES", appear dozens of miles above

4-Thermosphere

It extends from about 90 km (56 miles) to between 500 and 1,000 km (311 to 621 miles) above our planet.
Temperatures climb sharply in the lower thermosphere (below 200 to 300 km altitude), then level off and hold fairly steady with increasing altitude above that height. Solar activity strongly influences temperature in the thermosphere. The thermosphere is typically about 200° C (360° F) hotter in the daytime than at night, and roughly 500° C (900° F) hotter when the Sun is very active than at other times. Temperatures in the upper thermosphere can range from about 500° C (932° F) to 2,000° C (3,632° F) or higher.

5-Exosphere

Very high up, the Earth's atmosphere becomes very thin. The region where atoms and molecules escape into space is referred to as the exosphere. The exosphere is on top of the thermosphere.

Shaa-Baaz · #30 Tuesday, March 03, 2009

What causes a rainbow?

Although light looks colorless, it’s made up of many colors-red, orange, yellow, green, blue, indigo and violet. These colors are known as the spectrum. When light shines into water, the rays of light refract, or bend, at different angles. Different colors bend at different angles--red bends the least and violet the most. When light passes through a raindrop at a certain angle, the rays separate into the colors of the spectrum-and you see a beautiful rainbow.

Why do some objects, such as doors and windows, get bigger and smaller?

Have you noticed that closet doors don’t close as easily in the summer as they do in the winter? It’s because they expand in the heat of the summer and contract during the cold winter. Everything on Earth is made up of tiny particles called molecules, which are in constant motion. When the molecules heat up, they move faster, pulling apart from one another. As they move apart, they take up more space, causing even solid objects to grow slightly larger. Molecules slow down as they cool, and they take up less room. This causes things to shrink a little bit. (Water is an exception. When it freezes, the molecules line up in such a way that the ice takes up more space.)

Why do cats always land on their feet?

Cats owe some of their nine lives to their unique skeletal structure. Cats don’t have a collarbone, and the bones in their spine are more flexible than other animals. This makes it easier from them to bend and rotate their bodies easier during a short fall. A fall of two or more floors, however, can seriously injure a cat. A cat's feet and legs usually can’t absorb the impact of a fall from that distance or higher.

What makes popcorn pop?

A popcorn kernel is actually a seed. At its center is a tiny plant embryo, a life form in its earliest phase. The embryo is surrounded by soft, starchy material that contains water. Surrounding the embryo is a hard shell. When the kernel is heated to about 400 degrees Fahrenheit, the water turns to steam. The pressure from the steam causes the kernel’s shell to explode and the starch to spill out. You have to add the butter!

What causes lightning?

When air rises and falls within a thunderstorm, positive and negative charges form in the cloud. The bottom of the thundercloud has a negative charge, and the top has a positive charge. A flash of lightning happens when a charge becomes so strong that the air can’t stop it from jumping from the cloud to the ground, which has a positive charge. Lightning can also form inside the cloud, moving between the positively and negatively charged areas. The average flash of lightning could turn on a 100-watt light bulb for more than three months. The air near a lightning strike is hotter than the surface of the Sun.

Why do I feel dizzy when I spin?

Inside your ears are tubes filled with liquid. The liquid moves when you move, telling your brain what position your body is in. When you spin, the liquid also spins. The liquid continues to spin after you stop. Your brain thinks you’re still spinning, so you continue to feel that everything is going in circles-until the liquid stops moving.

Why does a knuckleball seem to “dance” toward home plate?

The ball drops and soars unpredictably because it doesn’t spin. The lack of rapid spin turns the seams of the baseball into tiny airfoils—surfaces that create lift and drag when they fly through the air. As the air passes over the seams, tiny swirls are created, causing pockets of low pressure around the surface of the ball. As air rushes in to fill the pockets, the ball is pushed in different directions. If the ball rotates too much, the seams will present a more consistent surface to the wind, and the ball will likewise follow a smoother path.

Why do leaves change color in the fall?

One of the sure signs of fall (besides the beginning of a new school year) is the change in color of leaves from green to bright yellow, orange and red. Trees are sort of like bears—they store up food during the spring and summer and then rest for the winter. Over the spring and summer, trees use a process called photosynthesis to make food and energy. A green pigment called chlorophyll makes photosynthesis happen. During the fall and winter, there isn’t enough light or water for photosynthesis to occur, so the chlorophyll begins to fade way. As the green disappears, the other colors begin to emerge. These colors were present in the leaves all along, but they were dominated by the chlorophyll

Why does my hair stand on end when I take off my hat on a cold, dry day?

Everything you see is made up of atoms. They contain even smaller particles, called protons and electrons. Protons have positive electrical charges and they never move. Electrons have a negative charge and they move around. Atoms usually have the same number of protons and electrons, so they cancel each other out and atom is neutral—it has no charge. When two things are rubbed together, sometimes the electrons move from one thing to the other. The atom that loses electrons becomes positively charged, and the atom that gets more electrons becomes negatively charged. Two things that have different charges pull toward each other; two things with the same charges push away from each other. When you take your hat off, electrons from your hat move on to your hair. Your individual hairs then have the same positive charge, so they move away from each other, and you look really funny.

How does a plane takeoff and fly?

It’s easy to understand how a bird can fly—it’s lightweight and has wings. But how does a huge airplane get off the ground? The plane’s engine pushes the plane forward. As it moves, air flowing around the wings creates lift. The lift increases as the plane gathers speed. The plane takes off once there’s enough lift to overtake gravity. When the plane’s in the air, thrust from the engines pushes the plane forward.

How do scientists know how to make a flu vaccine if viruses can be different every year?

The flu virus changes every year. However, scientists gather information about virus mutations, or changes, before the flu-virus season begins. This lets them predict what each year’s flu virus might look like. Based on that, a vaccine is made that we hope will be accurate enough to help people fight off major cases of the flu.

What are stem cells?

Stem cells, the basic building blocks of human development, are sometimes called “magic seeds.” That’s because they can regenerate human tissue of various kinds. The use of stem cells is controversial because the best source for the cells is human embryos. Stem cells form four to five days after an egg is fertilized. These embryos must be destroyed to harvest the cells, and those opposing the research consider this the same as taking human life. Those who support stem cell research say that an embryo that is just a few days old is simply a miniscule cluster of cells and not the same as a human life. They maintain that stem cells have the potential to save human lives. Stem cells show promise in being able to one day be able to treat and cure many illnesses and diseases, such as Alzheimer's, diabetes, Parkinson's, spinal cord injuries and other medical conditions.

Why do stars twinkle?

We see the stars through the atmosphere. Their light passes through millions of miles of constantly moving pockets and streams of air, which distort the image of the stars. Even though many stars are much larger than planets, they're so far away from us that they seem smaller, like tiny dots. The distortions make it seem as if the shining lights are moving or blinking. In outer space, where there is no atmosphere, stars don't twinkle.

What causes thunder?

When a bolt of lightning shoots through the atmosphere, it heats the air to an amazing 50,000 degrees Fahrenheit in a fraction of a second. The superheated air rapidly expands, cools and then contracts, causing shock waves. These shock waves create sound waves, which we hear as thunder.

Why don't the oceans freeze?

In the Arctic and Antarctic, the oceans do freeze. The ice cap at the North Pole is entirely over ocean; the ice, however, is only a few feet deep. Oceans don't freeze solid for because they contain a lot of water, which is constantly circulating around the world. In addition, water flowing from warmer oceans (and from areas near underground volcanoes) takes off some of the chill. Another important factor is that oceans contain salt water, which has a higher freezing point than fresh water.

Why do boats float?

A steel bar dropped into water sinks, but a huge boat made of steel floats. Why? Most of the space in the boat is taken up by air. The air makes the boat less dense than water. Objects of lesser density float on liquids of greater density. This is also why holes in the bottom of a boat cause it to sink: as air floods out of the boat and water rushes in, the overall density of the boat increases to become more dense than the surrounding water.

What's the difference between bacteria and virus?

Bacteria are tiny, one-celled living organisms that can only be seen with a microscope. They live and breed in warm, moist environments in the body and elsewhere, growing quickly and causing infection. Bacterial infections can usually be treated with an antibiotic. Viruses are smaller than bacteria and cannot be seen with a microscope. They grow inside the body and produce toxins (poisons) that can cause rashes, aches and fevers. Viruses cannot be killed with antibiotics.

Why do I have brown eyes?

The genes we inherit from our parents determine things like our height, looks, hair color and eye color. This passing of characteristics from parent to child is called heredity. If your mother has brown eyes, and your father has blue eyes, there’s a good chance you’ll have brown eyes. That’s because the brown-eye gene is dominant, and the blue-eye gene is recessive. The dominant gene usually prevails over the recessive one. It’s possible, however, for you to have blue eyes if both your parents have brown eyes. They probably inherited recessive blue-eye genes from their parents and passed them on to you.