Given, mass of bullet (mb)=10g=10×10−3kg Initial speed of bullet is v . Length of pendulum, I =0.5m Mass of bob, m=1kg Initial speed of bob, u=0 Final speed of bullet, vb=100ms−1 Final speed of bob for making complete circle at bottom, v′=√5gl Acceleration due to gravity, g=10ms−2 By using law of conservation of momentum mbub+mu=−mbvb+mv′ ⇒