Question

A bullet is fired form a rifle. If the rifle recoils freely, then the kinetic energy of the rifle will be

• A. Same as that of bullet
• B. More than that of bullet
• C. Less than that of bullet
• D. None of these

Answer 1

Answer: (C)

Less than that of bullet

For recoil of riffle, momentum will be conserved
$MV=mv$
$\frac{K.Eofriffle}{K.Eofbullet}=\frac{\frac{1}{2}M{V}^2}{\frac{1}{2}m{v}^2}$
$={\frac{M}{m}\times \left(\frac{m}{M}\right)}^2=\frac{m}{M}$
As m < M, kinetic energy of riffle < kinetic energy of bullet.