Question

A bullet of mass $0.04kg$ moving with a speed of $90m{s}^{-1}$ enters a heavy wooden block and is stopped after a distance of $60$ cm. What is the average resistive force exerted by the block on the bullet?

Answer 1

The retardation of the bullet is given as,

$a=-\frac{u^2}{2s}$

$=-\frac{90\times 90}{2\times 60\times 10{}^{-2}}$

$=-6750m/s^2$

The retarding force is given as,

$F=-ma$

$=0.04\times 6750$

$=270N$

Thus, the average resistive force is $270N$.