Question

A stone dropped from the window of a stationary train hits the ground and comes to rest. An identical stone is dropped from the window when the same train is moving with speed v and it comes to rest on the ground. Assume that in each case, the entire energy lost in impact goes into heating the stone. Then:

• A. The first stone is slightly more heated than the second
• B. The second stone is slightly more heated than the first
• C. Both the stones will be raised to the same temperature
• D. The second stone will be slightly more heated than the first only if its horizontal speed during fall is more than the final vertical speed

Answer 1

The correct option is B The second stone is slightly more heated than the first

When stone A is dropped it has only potential energy $mgh$, when it reaches the ground.

That energy is given by,

$Energy=mgh$ (1)

When second particle is dropped from moving train then it has both potential energy and kinetic energy and is given by,

$Energy=mgh+\frac{1}{2}m{v}^2$ (2)

$v=$ velocity of particle when dropped from moving train with speed $v$

So, energy is more in second case and it goes into heating the stone.

Therefore second stone is more heated than the first.