In Example 9.6, we treated the merry-go-round plus child as a system (Fig. 9.13) who...

In Example 9.6, we treated the merry-go-round plus child as a system (Fig. 9.13) whose angular momentum is conserved. The merry-go-round is initially at rest, so its initial angular momentum is zero, but at the end it is rotating, so its final angular momentum is nonzero. The angular momentum of the merry-go-round alone thus changes, which can only happen if there is a torque on the merry-go-round.

What force provides this torque?

(a) The force of gravity on the merry-go-round

(b) The force of air drag on the merry-go-round

(c) The force produced by the child when she jumps off

(d) The force of friction at the axle of the merry-go-round

(reference figure 9.13)

(reference example 9.6)