Correct answer is:- (b) -50 N
Explanation :-
Mass of bullet, m = 0.01 kg
Time taken by the bullet to come to rest, t=0.02 s
v = u + at
⇒ 0 = 100 + (0.02) (a)
⇒ a = -5000 m/s-2
Retarding force exerted by the wooden block, F = ma
∴ F = -5000 × 0.01 = -50 N