A bullet of mass m=50 gm strikes (Δt≈0) a sand bag of mass M=5 kg hanging from a fixed point, with a horizontal velocity →vp. If bullet sticks to the sand bag then just after collision the ratio of final and initial kinetic energy of the bullet is?
According to Conservation of Momentum,
mvp = (m+M)V where
m is the mass of the bullet,
vp is the velocity of the bullet before collision,
M is the mass of the sandbag and V is the velocity after the collision
0.05* vp = (0.050+5)V
vp = [5.050/0.05] V = 101 V
Ratio of final KE to initial KE = [0.5mV2] / [0.5mvp2] =
10‑4 (approx.)