Problem Diagram 

Billy and Susan just received toy cars from their grandparents. Billy's
car was a sportscar model and Susan's was a box car model. Whose car
will run fastest downhill?
What is known:
 Each car body weighs 10 lb.
 The wheels on both cars weigh 1 lb each.
 The cars are rolled down a 13.7 ft hill.
 The sports car comes with rim wheels that have nearly all of the wheel's
mass at the rim.
 The box car comes with wheels that are uniform disks, with the mass
evenly distributed throughout.
