When you drop a pebble from height H, it reaches the ground with speed V if there is no air resistance. From what height should you drop it so it will reach the ground with twice speed?
A) $\sqrt { 2 }$ H
B) 2H
C) 4H
D) 8H
E) 16H

Question

Quizplus · Accepted Answer

The speed of the pebble is proportional to the square root of the height from which it is dropped. To double the speed, the height must be quadrupled, hence 4H.

When You Drop a Pebble from Height H, It Reaches 2\sqrt { 2 }2​

When You Drop a Pebble from Height H, It Reaches $\sqrt { 2 }$