A pair of bumper cars in an amusement park ride collide elastically as one approaches the other directly from the rear (see figure). One has a mass of 250kg and the other 300kg, owing to differences in passenger mass. If the lighter one approaches at 7.0 m/s and the other is moving at 3.5 m/s, calculate

a.  (15 points)

their velocities after the collision, and
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

b.  (10 points)

the change in momentum of each.