### torque

ROTATION OF RIGID BODY

FIGURE 2.1(a) shows three children are playing on a merry-go-round which has a

moment of inertia of 271 kg m2

. Once the children get the merry-go-round spinning,

they stand evenly spaced around the outer edge as shown in FIGURE 2.1(b). Each

child has a mass of 28.0 kg, and the merry-go-round has a radius of 2.10 m.

(a) Assuming the moment of inertia of a child’s mass on the edge of the disc is

given by 𝐼 = 𝑚𝑟

2

, calculate the moment of inertia of the system.

[3 marks]

(b) While the merry-go-round is rotating at 2.31 m s-1

, one child drags her foot on

the ground to bring the merry-go-round to a stop in 2.80 s. Calculate the amount

of torque produced by the foot.

[3 marks]

(c) The children get the merry-go-round spinning once again at a constant angular

speed. Then each child moves inward towards the centre of the merry-go-round.

Using physics principles, explain the effect this has on rotational motion of the

merry-go-round.