Review 1. What units would you use to describe the speed of a
car? Would you use different units for the speeds of
runners in a neighborhood race? Explain.
2. In a skateboarding marathon, the winner covered 435 km
in 36.75 h. What was the winner's average speed?
3. Think Critically: Make a distance-time graph for a
2-hour car trip. The car covered 50 km in the first
30 minutes, stopped for 30 minutes, and covered 60 km
in the final 60 minutes. Note the three graph segments.
Which graph segment slopes the most? Which one does
not slope? What was the car's average speed?

Amerry-go-round of radius r, shown in the figure, is rotating at constant angular speed. the friction in its bearings is so small that it can be ignored. a sandbag of mass m is dropped onto the merry-go-round, at a position designated by r. the sandbag does not slip or roll upon contact with the merry-go-round. how would you rank the following different combinations of m and r on the basis of the angular speed of the merry-go-round after the sandbag "sticks" to the merry-go-round from largest to smallest. a) m = 10kg, r = 0.25r b) m = 20kg, r = 0.25r c) m = 10kg, r = 0.50r d) m = 10kg, r = 1.0r e) m = 15kg, r = 0.75r f) m = 40kg, r = 0.25r