1. Why the front wheels of vehicle lean outwards slightly ?

Answer: As viewed from the front or rear of the vehicle, camber refers to the "lean" of the wheel from top to bottom. A wheel that leans outward at the top (compared to true vertical) has positive camber. One that leans inward at the top has negative camber. If the wheel is oriented in a true vertical, it's called zero camber.
Camber must always be adjusted to maximize the tread contact patch based on the driving requirements. In most cases, OE specifications will recommend a slightly positive or zero camber to maximize tire wear and traction, and to provide easier steering and greater resistance to directional darting in a straight line.
If the wheel features a static negative camber angle (vehicle sitting idle), this places more tread load at the road surface on the inner shoulder and tread area. Negative camber is regularly employed on performance vehicles (especially race cars on road courses) in order to increase the tire contact patch during hard turns. Since lateral loading (when a car goes into a hard turn) will try to push the top of the inside tire outward, an adequate negative camber angle may compensate for this. So, while the front wheels may display negative camber as the vehicle rolls light, when it goes into a hard turn, ie wheel facing the direction of the turn will try to "straighten up," achieving maximum tread contact with the road. If camber isn't sufficiently negative, this tire would lean too far, causing the inside of the tread to lift and placing excess stress and load only on the outside of the tread and outer shoulder.

Sound is generated in the larynx, and that is where pitch and volume are manipulated. The strength of expiration from the lungs also contributes to loudness, and is necessary for the vocal folds to produce speech.
Fine manipulation of the larynx is used in a great way to generate a source sound with a particular fundamental frequency, or pitch. This source sound is altered as it travels through the vocal tract, configured differently based on the position of the tongue, lips, mouth, and pharynx. The process of altering a source sound as it passes through the filter of the vocal tract creates the many different sounds.
The vocal folds can be held close together (by adducting the arytenoid cartilages), so that they vibrate (see phonation). The muscles attached to the arytenoid cartilages control the degree of opening. Vocal fold length and tension can be controlled by rocking the thyroid cartilage forward and backward on the cricoid cartilage, and by manipulating the tension of the muscles within the vocal folds. This causes the pitch produced during phonation to rise or fall.

It is highly unlikey to find all these voluntary and involuntry movements taking place to produce sound similar in all individuals. That is why, people voices sound differently.

4. Why is an electric bulb less efficient than a fluorescent tube ?

Answer: My dear, in ordinary electric bulb, electic energy is being converted into light energy and heat energy as the tungston filament resists to the flow of electricity and gets hoter and glows.
A fluorescent lamp is a gas-discharge lamp that uses electricity to excite mercury vapor in argon or neon gas, resulting in a plasma that produces short-wave ultraviolet light. This light then causes a phosphor to fluoresce, producing visible light.
The main principle of fluorescent tube operation is based around inelastic scattering of electrons. An incident electron (emitted from the coils of wire forming the cathode electrode) collides with an atom in the gas (such as mercury, argon or krypton) used as the ultraviolet emitter. This causes an electron in the atom to temporarily jump up to a higher energy level to absorb some, or all, of the kinetic energy delivered by the colliding electron. This is why the collision is called 'inelastic' as some of the energy is absorbed. This higher energy state is unstable, and the atom will emit an ultraviolet photon as the atom's electron reverts to a lower, more stable, energy level. The photons that are released from the chosen gas mixtures tend to have a wavelength in the ultraviolet part of the spectrum. This is not visible to the human eye, so must be converted into visible light. This is done by making use of fluorescence. This fluorescent conversion occurs in the phosphor coating on the inner surface of the fluorescent tube, where the ultraviolet photons are absorbed by electrons in the phosphor's atoms, causing a similar energy jump, then drop, with emission of a further photon. The photon that is emitted from this second interaction has a lower energy than the one that caused it. The chemicals that make up the phosphor are specially chosen so that these emitted photons are at wavelengths visible to the human eye. The difference in energy between the absorbed ultra-violet photon and the emitted visible light photon goes to heat up the phosphor coating.
The principle working in fluroescent tube is more efficient and this is the answer to your question.

Question 5. All motions are relative to one another ?

Answer: This belongs to the theory of relativity. Whenever you observe the motion of an object, your observations are relative to your own frame of reference. Let me give you an example. You are traveling in your car and your mobile phone is lying on the dash board. Movement is defined by the change in displacement. The distance between you and your mobile phone is not changing and hence you will observe that the mobile is not moving. Now you pass by a pedestrian walking on the footpath. The distance between him and your mobile phone is changing. So according to him, your mobile phone is moving. So the movement is always relative to the frame of reference. Since your frame of reference and that of the pedestrian were different, so the observations were different.

6. Transmission lines carry very high voltages ?

Voltage is simply the potential difference. At higher potential difference, electricity can be transferred more efficiently. That is why, the potential difference is kept higher when electricity is to be transferred to remote areas.