Question

A: when we jump on to a Cushion we get less hurt. R: when change in momentum of an object takes place in more time it experiences less force.

To drive a nail into a wooden block, we blow a hammer on the nail. When a ball hits a wall, it bounces back In both of these examples, a large force acts for a very short duration producing a finite change in the momentum of the body. Here it is difficult to measure force and time separately. The product of the force and time that produces a finite change of momentum is called impulse. Impulse = Force x time duration = Total change in momentum. SI unit of impulse is Ns or kgm/s. It is a vector quantity having the direction same as that of force or the change in momentum. A large force acting force a short time is called an impulsive force. For a variable force, impulse J is given by J = P2 - P1 = ∫dp = ∫Fdt = Area under the force-time curve.

A ball is dropped from height h. The velocity attained by the ball just before reaching the ground is

ASSERTION: When a body is dropped or thrown horizontally from the same height it would reach the ground at the same time REASON: Horizontal velocity has no effect on the vertical motion