Question

A heavy stone is thrown in from a cliff of height h in a given direction. The speed with which it hits the ground
(a) must depend on the speed of projection
(b) must be larger than the speed of projection
(c) must be independent of the speed of projection
(d) may be smaller than the speed of projection.

Answer 1

Answer:

(b) must be larger than the speed of projection

Explanation:

(b) must be larger than the speed of projection

Answer 2

The speed with which it hits the ground must depend on the speed of projection.

Explanation:  

Since Kinetic Energy given to the stone depends on the projection speed.

And the speed with which it hits the ground depends on the kinetic energy provided to the stone at the time of the projection, so respond (a).

When the stone transfers its kinetic energy to the ground is the sum of the kinetic energy given to it at the time of projection and the potential energy at the ground projection.

This means the stone's kinetic energy is more at ground level than at projection stage.

Since kinetic energy of a given mass particle is only dependent on its speed, so its speed when it hits the ground must be larger than the speed of projection.

Hence (b). (c) and (d) are opposite to the above condition, hence not true.