Question

A 5.5 g bullet moving at 120 m/s strikes a thick wall. Assume that the bullet

undergoes a uniform deceleration and stops after penetrating 6 cm within the wall. Find

(a) The time taken by the bullet to stop.

(b) The impulse on the wall.

(c) The magnitude of the average force experienced by the wall

Answer 1

(a) $S=v^2/(2a)\to a=v^2/(2S)=120^2/(2\cdot0.06)=$

$=120000\ (m/s^2)$

$v=v_0-at\to t=v_0/a=120/120000=0.001\ (s)$

(b)$\ \ p=mv=0.0055\cdot120=0.66\ (kg\cdot m/s)$

(c) $F=\Delta p/\Delta t=0.66/0.001=660\ (N)$