**Solution**:

H_{1} =10 m, v_{1} =?

Loss of energy =40% H_{2} =?

On striking the floor, K.E = P.E

½ mv_{1}^{2} = mg H_{1}

V_{1 }= ?(2gH_{1})= ?( 2x9.8x10)

V_{1}= ?196= 14 m/s

As the body loses 40% of its energy, final energy E_{2} =( 60/100) of initial energy

i.e. mgH_{2} = (60/100)mgH_{1}

H_{2} =3/5 H_{1}= (3/5)X10= **6m**