A bullet of mass of 30g and travelling at a speed of 200msˉ¹ embeds itself in a wooden block. The bullet penetrates a distance of 12cm into the wood. Using the concepts of work done by a force and kinetic energy, determine the average resistive force acting on the bullet.

Answer 1

Kinetic energy = work of resistive force
mv^2/2= W= F•s•cosα
cosα = 1
F= mv^2/2•s=0.03•(200)^2/2•0.12=5000 N

Answer 2

Kinetic energy = work of resistive force
mv^2/2= W= F•s•cosα
cosα = -1(α=180 deg.)
-F= mv^2/2•s=0.03•(200)^2/2•0.12=5000N