A body of mass 20 kg is initially at a height of 3 m above the ground. It is lifted to a height of 2 m from that position. Its increase in potential energy is :

400 J

\(U_{initial} = mgh = 20*10*3 = 600 \text{ J}\)

\(U_{final} = mgh' = 20*10*5 = 1000 \text{ J}\)

\(\Delta U = U_{final} - U_{inital} = 1000 \text{ J} - 600 \text{ J}\)

\(\Delta U = 400 \text{ J}\)