Question

a body is dropped from height h when loss in its potential energy is u then its velocity is v.the mass of body will be

Answer 1

Let the mass of body be 'm' 

According to the conservation of mechanical energy 

Loss in potential energy = gain in kinetic energy 

U = 1/2 mv²

m = 2U/v²

Answer 2

According to conservation of energy
Initial Total energy = Final Total energy
U = 0.5mv²

From above
m = 2U / v²

Mass of the body is 2U / v²