Question

A bullet of 10 g strikes a sand bag at a speed of 10³ ms^-1 and gets embedded after travelling 5 cm. Calculate (i) the resistive force exerted by the sand on the bullet. (ii) the time taken by the bullet to come to rest.

Answer 1

Dear Student,


$$\begin{gathered} Given, \\ m=10g={10}^{-2}kg \\ s=5cm=0.05m \\ u={10}^{3}m/s \\ v=0\left[comestorest\right] \\ Thirdequationofmotion: \\ {v}^2-u^2=2as \\ 0-{\left({10}^3\right)}^2=2a\times 0.05 \\ a=-\frac{{10}^6}{0.1}={10}^{7}m/s^2 \end{gathered}$$
$$\begin{gathered} F=ma={10}^{-2}\times {10}^7=-{10}^{5}N \\ Forceonbulletis-{10}^{5}Nsotheresistiveforceis{10}^{5}N \end{gathered}$$

$$\begin{gathered} Also, \\ v=u+at \\ 0={10}^3+(-{10}^7)t \\ t=\frac{{10}^3}{{10}^7}={10}^{-4}sec \end{gathered}$$



Regards,