Question

A bullet of mass 0.2 kg, moving with a velocity of 200 ms⁻¹, strikes a stationary wooden target of mass 5 kg. If all the energy is transferred to the wooden target, calculate the velocity with which the target moves in the forward direction.

Answer 1

First find the bullet's kinetic energy:

\[ K_{\text{bullet}} = \frac{1}{2}\, mv^{2} \]

\[= \frac{1}{2} \times 0.2 \times 200^{2} \]

= 4000 J

All this energy is transferred to the target. If its velocity is v, then

\[ \frac{1}{2} \times 5 \times v^{2} = 4000 \]

\[ v^{2} = \frac{4000 \times 2}{5} \]

v² = 1600

v = 40 m s⁻¹

The target moves forward at 40 m s⁻¹.