A rock is dropped from rest from a height h above the ground. It falls and hits the ground with a speed of 11 m/s. From what height should the rock be dropped so that its speed on hitting the ground is 22 m/s? Neglect air resistance.
A)1.4h
B)2.0h
C)3.0h
D)4.0h
E)0.71h

Question

Quizplus · Accepted Answer

The speed of the rock is proportional to the square root of the height from which it is dropped. Doubling the speed requires quadrupling the height, so the height should be 4.0h.

A Rock Is Dropped from Rest from a Height H