Question

A bullet initially moving with a velocity 20 m/s strikes a target and comes to rest after penetrating a distance 10 cm in the target. Calculate the retardation caused by the target.

Answer 1

Here, u=20m/s
v=0 as the bullet comes to rest
s=10cm=0.1m
a=?
We know that,
v^2 = u^2 +2as
0=20^2 +2a×0.1
0=400+0.2a
-400=0.2a
therefore, a=-400/0.2=-2000m/s^2
minus sign indicates that it is retardation.
therefore, a=2000m/s^2