Question

An object of mass 4 kg is raised to height of 5 m above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half way down.

Answer 1

m = 4 kg, h = 5 m, g = 10 m/s². 

Potential energy = mgh = 4 × 10 × 5 = 200 J.

 If object is allowed to fall, then we have to take half of distance. 

u = 0, h = 2.5 m, a = + g = 10 m/s² 

v² — u² = 2gh ⇒ v² = 2 × 10 × 2.5 ⇒ v² = 50

∴ At half of distance the kinetic energy = 100 J.