a line frm hc verma "A vehicle accelarates on the road only bcz the frictional force on the vehicle due to road drives it".what is this? How? Please explain.

Dear Krish Mishra,

The force of friction always opposes the relative motion. 

When a force is applied to a ball or wheel, it will start rolling, provided there is a resistive force preventing the wheel from simply sliding along the other surface. The force may be a torque applied to the axle of the wheel or a linear push or pull on the wheel. The resistance of static friction causes the rolling motion. If the wheel or tire has treads and the other surface is soft, then those treads provide extra friction known as traction.

Note that the friction required to start rolling motion is not rolling friction, which is defined as the friction slowing down rolling motion.

According to the law of conservation of energy, no energy should be lost due to friction. The kinetic energy lost is transformed primarily into heat and/or motion of other objects and fluids. An airplane will heat and accelerate the air as it passes. A submarine will do the same to the water. In some cases, the "other object" to be accelerated may be the Earth. A sliding hockey puck will come to rest due to friction both by changing its energy into heat and accelerating the Earth in its direction of travel (by an immeasurable amount).

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