8.3 Exercise 5

Cart A is moving with an initial velocity +v (in the positive direction) toward cart B, initially at rest. Both carts have equal mass and are on a frictionless surface. Which of the following statements correctly characterizes the velocity of the center of mass of the system before and after the collision?

1. $\frac{+ v}{2}$ before, $\frac{- v}{2}$ after
2. $\frac{+ v}{2}$ before, 0 after
3. $\frac{+ v}{2}$ before, $\frac{+ v}{2}$ after
4. 0 before, 0 after