for the clarification of all:

this is a concept of physics called "moments and forces". for a rider to sit on bicycle, the weight of the rider must be balanced by all forces at the wheels.

let us assume that:

W = weight of the rider.
Df = distance between the front wheel and the seat.
Dr = distance between the rear wheel and the seat.
Ff = Force on the front wheel.
Fr = Force on the rear wheel.

Assume that the bicycle's weight is zero.

now for the cycle to be balanced:

W X Dr = Ff X Dr + Ff X Df

if the distance is equal between the seat, then:

Dr = Df

so the formula will become

W X Dr = Ff X Dr + Ff X Dr

=> W = Ff + Ff

which means W = 2 Ff

Ff = W/2 which means Force on front wheel is half the weight. Thus force on the back wheel will be half the weight too.

The answers will different if the distances are different.

Is that enough Redmax

Sure sir... We'd try hard to grasp the assumptions coming from an engineer's mind, not instrument :p. (Kidding Jiger)

Let's analyze this one. It has really got my head spinning.

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Verily, His command, when He intends a thing, is only that He says "Be!" - and it is! (Al-Quran)

More than enough Jiger.

You know what, at times physics and its problems/equations etc seem quite weird to me.

Thanks to EDS paper setter, he doesn't include this yet.

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Verily, His command, when He intends a thing, is only that He says "Be!" - and it is! (Al-Quran)

the north pole of the magnet directs itself to the north pole of the earth and the south will align itself to the south pole...

lemme rephrase it....the north pole of the magnet points to the north pole of the earth but then the north pole of the earth is basically the magnetic south pole

i hope that clears the situation

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Umar Abbas Babar
I Know I am Bad But When Bad is the Best, Bad is the Only Choice

Jiger your answer is right as per the book.

Can you explain why it is so? I mean why would they attract each other? Does it have anything to do with gravity or they got some other force to pull one an other? Would it matter if they didn't do so ? I might sound weird either but trust me questions as such keep popping up in my mind and I simply don't find a satisfactory answer.

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Verily, His command, when He intends a thing, is only that He says "Be!" - and it is! (Al-Quran)

okay brother...

http://http://www.physics.sjsu.edu/b...ar_magnets.JPG
here is the explanation...

http://http://wpcontent.answcdn.com/...fusion.svg.png

check out these images

we assume that there are some unseen attractive forces coming out of the north pole which end up at the south pole. so as per the above diagram, if a south pole is brought near to the north pole, the rays going out of the north pole ends up in that south pole of the magnet. thus bringing it closer to itself or in other words attracting it.

if two like poles like north and north or south and south face eachother then these rays get distorted and thus they are repelled. for example two norths: rays are going out of both. so there is this push from one north and a push from the other north and the distance increases..same happens for the two souths, rays (magnetic lines) get distorted and they are thrown further apart.

Gravity does not have to do anything with it. Gravity is a property of mass. anything that has some mass will have gravity. believe it or not, you and your PC exert force of gravity on each other but that's too small to notice. the earth is very big compared to us and its mass is more so its gravity is noticeable. while the sun is bigger than us all so it attracts us all.

Magnetism is a property of some specific types of matters. in general words, ferromagnetic substances (iron and some other). in earth's core, ferromagnetic substances are in molten form. due to revolutions of earth, they are spinning inside, thus they are generating these magnetic fields.

now because to us a magnetic pole is more reliable/wanted thus the pole pointing to our Geographic north pole is called a north pole and we assume that there is an imaginary south pole over there called geomagnetic south pole. vice versa for the south pole..

thus geographic north pole = geomagnetic south pole

i hope i was of some service !

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Umar Abbas Babar
I Know I am Bad But When Bad is the Best, Bad is the Only Choice

yes dear, you are absolutely a great help. Thanks for that.


Just one question remains... Would it matter if they didn't attract each other?
If you are sleepy since its very late, you may answer it in morning or any other time. I'm no haste.

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Verily, His command, when He intends a thing, is only that He says "Be!" - and it is! (Al-Quran)

well if magnetism could utter a few words, i am sure its reply would have been:

"Duboya mujh ko honay nay,
Na mey hota tou kia hota"
heheh..kidding!

yes brother magnetism helps us alot in many ways:

1- it is used in our certain electrical appliances like: MICROWAVE OVEN. the magnetic field generated by the oven turns/attracts/repels the charged particles in our food to heat them up

2- it is used in transformers.

3- it is used in bells.

4- furthermore earth's magnetic cover is very important for our life on this earth. they deviate many charged particles from the suns rays i.e. change their direction so that they won't hit this planet. that may cause skin cancer and other diseases and not to mention play havoc with our power distribution systems and other entities.

so everyday we humans using many things which directly/indirectly rely on magnetism or use magnetism. so magnetism is important to us...

ooppss!! i have to go to bed now ...subah office bhi jana hay...thrown in more questions if you like to..i will answer them in the morning inshallah..!!

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Umar Abbas Babar
I Know I am Bad But When Bad is the Best, Bad is the Only Choice

@umarabbas
this means if heat lost from flsk it take place by convection and radiation.
am i right?
1 more prob in same question flask iner surface is made of shining material why it is made so??
waiting for rply

Dear, the flask will lose its heat energy to the surroudings through Conduction and Radiation (normally). For example: The flask losing energy to the table on which it is put is conduction and radiation is when it looses its energy to the surroundings.

We need a perfect insulator inside the flask. that's why we see that special spongy type material used in flask. they ensure that little heat is lost via conduction and radiation. the inner part is made shining so as to make the heat energy reflect within the flask. Shinny substances reflect most of the heat and absorb very little. A perfect example could be placing a mirror and a frying pan of steel in the sunlight. it will be observed that the mirror's temperature would be far lesser than the frying pan's temperature. Reason as i stated earlier is that the mirror absorbs less heat and reflects most of it...

i hope i was clear about it!

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Umar Abbas Babar
I Know I am Bad But When Bad is the Best, Bad is the Only Choice