Question

Suppose you are standing on the center of a merry-go-round that is at rest. You are holding a spinning bicycle wheel over your head so that its rotation axis is pointing upward. The wheel is rotating counterclockwise when observed from above. For this problem, neglect any air resistance or friction between the merry-go-round and its foundation.
Suppose you now grab the edge of the wheel with your hand, stoping it from spinning. What happens to the merry-go-round?
A. It remains at rest
B. It begins to rotate counterclockwise
C. It begins to rotate clockwise

Answer 1

Answer:

B. It begins to rotate counterclockwise

Explanation:

It can happen that the merry-go-round remains at rest in the case when the person is standing on the axle  of the merry go round whose axis is fixed to some rigid support, but here the person is standing at the center of the merry-go-round not at the axle hence the according to the conservation of angular momentum. Angular momentum is given as:

$L=I.\omega$

for the conservation of momentum

$I.\omega=I'.\omega'$

where:

$I=$ moment of inertia of the merry-go-round

$\omega=$ angular velocity of the merry-go-round

$I'=$ moment of inertia of the bicycle wheel

$\omega'=$ angular velocity of the wheel

As the person tries to stop the wheel which is rotating then the person feels an opposing force which tries to moves the whole system in its direction.