Question

A bullet of mass 0.04 kg moving with velocity of 400 m/s strikes a wooden planks and emerges with velocity of 200 m/s . What is the work done by the bullet passing through the plank

Answer 1

$m = 0.04kg \\ v = 200m.s \\ u = 400m.s \\ \\ work \: done = change \: in \: energy \\ = \frac{1}{2}m {u}^{2} - \frac{1}{2} m {v}^{2} \\ = \frac{1}{2}m( {u}^{2} - {v}^{2} ) \\ = \frac{1}{2} \times 0.04(( {400})^{2} - ( {200})^{2} ) \\ = \frac{1}{2} \times 0.04((400 + 200)(400 - 200)) \\ = \frac{1}{2} \times 0.04(600 \times 200) \\ = 0.04 \times 300 \times 200 \\ = 2400joule$