Question

Two masses of 4 kg and 1 kg are moving in opposite direction with equal kinetic energies of 8 J. If the collision
between the masses are perfectly inelastic the percentage loss of kinetic energy of the masses is

• A. 60%
• B. 70%
• C. 80%
• D. 90%

Answer 1

The correct option is D 90%

Kinetic energy, $k=\frac{1}{2}m{v}^2{v}_1=\frac{2m}{s}and{v}_2=4m/s$
Now $4\times 2-1\times 4=(4+1)v\Rightarrow v=\frac{4}{5}\therefore \frac{\Delta k}{k}\times 100=\left[\frac{8\times 9}{16\times 5}\right]\times 100=90$