Question

A bullet of mass 10g strikes a wooden block with velocity of 300m/s after penetrating 20cm into it, it's velocity drops to 200m/s. Then average resistance offered by the block is

Answer 1

V^2 = Vo^2 + 2a*d = 200^2.
300^2 + 2a*0.2 = 40,000,
0.4a = 40,000-90,000 = -50,000, a = -125,000 m/s^2.

F = M*a = 0.01 * (-125000) = -11250 N. Resisting the bullet.

Answer 2

Correction: F = -1250 N.