A bullet of mass 0.04 kg moving with a speed of `90 m 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?

Explanation

The retardation ‘a’ of the bullet (assumed constant) is given by
`a = ( -u^2)/(2s) = (-90 xx 90)/(2 xx 0.6) ms^(-2) = - 6750 ms^(-2)`
The retarding force, by the second law of motion, is
`= 0.04 kg xx 6750 m s^(-2) = 270 N `
The actual resistive force, and therefore, retardation of the bullet may not be uniform. The answer therefore, only indicates the average resistive force.