Q. A bullet of mass 50 g is fired from a gun of mass 2 kg. If the total kinetic energy produced is 2050 J, the kinetic energy of the bullet and the gun respectively are
A) 200 J, 5 J
B) 2000 J, 50 J
C) 5 J, 200 J
D) 50 J, 2000 J
Explanation
(b) Since there is no external force acting on rifle bullet system, hence
$p_{b} = p_{g}$ and hence $\frac{K_{b}}{K_{g}} = \frac{m_{g}}{m_{b}} = \frac{2kg}{50g} = \frac{4}{1}$
Or $K_{g} = \frac{K_{b}}{4}$
Now total energy $K_{b} + K_{g}\ $ or $+ \frac{K_{b}}{40} = \frac{41}{40},K_{b} = 2050$
$\Rightarrow \ \ K_{b} = \frac{2050 \times 40}{41} = 2000$J
And $K_{g} = 2050 - 2000 = 50$J.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.