Question

A bullet fired into a block loses half its velocity after moving $0.9$m. Before it comes to rest, distance travelled would be:

• A. $1.2$ m
• B. $0.3$ m
• C. $2.0$ m
• D. $1.6$ m

Answer 1

The correct option is B $0.3$ m

Given initial velocity = $v$ m/s and final velocity =$\frac{v}{2}$ m/s after traveling a distance of $0.9$ m

From equation of motion we get,

$v^2=u^2+2asa=\frac{v^2-u^2}{2s}=\frac{{\frac{v}{4}}^2-v^2}{2s}=-\frac{3v^2}{8s}$

Now distance covered before coming to rest i.i when final velocity =$0$ m/s,

$s=\frac{v^2-u^2}{2a}=\frac{{-\frac{v}{4}}^2}{2(-\frac{3v^2}{8s})}=0.3m$