Question

A bullet of mass 20g moving with the speed of 120ms^-1 hits a thick muddy wall and penetrates into it. It takes 0.03s to stop inside the wall. Find (a) acceleration of the bullet in the wall (b) the force exerted by the wall on the bullet (c) force exerted by the bullet on the wall (d) the distance covered by the bullet inside the wall.

Answer 1

Mass of the bullet =20g or 0.02kg

initial velocity of the bullet(u)=120m/s

final velocity(v)=0m/s (because the bullet eventually stops)

a) Acceleration = (v-u)÷t

    = (0-120)÷0.03

    = -120÷0.03

    = -4000m/s²→Acceleration

Or it can be said that the bullet is retarding at 4000m/s²

b) Force=mass × acceleration

    Force exerted by wall on bullet= 0.02kg×4000m/s²

    =80 Newton

c)Answer will be the same...80 Newton. Every action has an equal and opposite reaction. Just the direction will be opposite.

d) Distance covered = speed×time taken

    =120m/s×0.03 seconds

    =3.6 m.