A ball with mass m and velocity V collides with a static B ball with mass 3M. The collision may be elastic or inelastic, so the velocity of B ball may be () A. 0.6vB. 0.4vC. 0.2vD. 0.1v

A ball with mass m and velocity V collides with a static B ball with mass 3M. The collision may be elastic or inelastic, so the velocity of B ball may be () A. 0.6vB. 0.4vC. 0.2vD. 0.1v

A. If VB = 0.6V, the direction of V is positive, and from the conservation of momentum, we get: MV = MVA + 3M · 0.6V, VA = - 0.8V, the total kinetic energy of the system before collision is EK = 12mv2. After collision, the total kinetic energy of the system is: EK ′ = 12mva2 + 12 · 3mvb2 = 12m (0.8V) 2 + 12 · 3mvb2 > 12mv2