A block of mass m1 moving with speed v1 undergoes a completely inelastic collision with a stationary block of mass m2. The blocks then move, stuck together, at speed v2. After a short time, the two-block system collides inelastically with a third block, of mass m3, which is initially stationary. The three blocks then move, stuck together, with speed v3. All three blocks have nonzero mass. Assume that the blocks slide without friction.
Find v2v1, the ratio of the speed v2 of the two-block system after the first collision to the speed v1 of the block of mass m1 before the collision.