a man drops 10kg rock from the top of a 5m ladder. wht is its speed just before it hits the ground? wht is its kinetic energy wen it reaches da ground.
Height from which the rock is dropped, h = 5 m
Mass of the rock, m = 10 kg
Acceleration due to gravity, g = 10 ms-2
Potential energy of the rock at this height, PE = mgh = 10 × 10 × 5 = 500 J
When the rock reaches the ground its entire PE is converted to KE.
So, the kinetic energy when it reaches the ground is 500 J.
Let, ‘v’ be the speed of the rock just before hitting the ground.
So, the speed of the rock just before hitting the ground is 10 ms-1