Question

A 35 g bullet strikes a 5 kg stationary block and embeds itself in the block. The block and bullet fly off together at 8.6 m/s What was the original speed of the bullet?

Answer 1

Hi there!

We can use the conservation of momentum for a perfectly inelastic collision to solve.

`m_1v_1 + m_2v_2 = v_f( m_1+ m_2)`

m1, v1 = mass and velocity of bullet (0.035 kg and ? m/s respectively)

m2, v2 = mass and velocity of block (5 kg and 0 m/s respectively)

vf = combined final velocity (8.6 m/s)

Plug in the givens and solve:


`0.035 (v_1) + 5(0) = 8.6(0.035 + 5)\\ \\ 0.035v_1 = 43.301\\ \\ v_1 = (43.301)/(0.035) = \boxed{1237.17 (m)/(s)}`