Question

A man drop a 10 kg rock from the top of a 5m ladder. What is its speed just before it hits the ground? What is its kinetic energy when it reaches the ground?

Answer 1

Mass of rock = 10 kg 

Height of ladder, h = 5m 

Initial velocity of rock, u = 0 

Final velocity, v 

g = 10 m/s² 

Using third equation of motion 

v² – u² = 2gh 

v = 10 m/s 

KE = 1/2 mv² = 500J