Question

A bullet fired into a fixed target loses half of its velocity after penetrating 3cm. How much futher it will penetrating before coming to rest assuming that it faces constant resistance to motion.

Answer 1

Let initial velocity of the bullet = u
After penetrating 3 cm its velocity becomes = u/2
From v2 = u2 - 2as
(u/2)2 = u2 - 2as
Thus, a  = u2/8
Let further it will penetrate through distance x and stops at some point
.0 =  (u/2)2 - 2 (u2/8)x
Therefore, x = 1 cm