Question

Spinning situations???
Can someone please answer this please and explain the reasoning behind it? 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, stopping it from spinning. What happens to the merry-go-round?
a. It remains at rest.
b. It begins to rotate counterclockwise (as observed from above)
c. It begins to rotate clockwise (as observed from above). Thank you!!!

Answer 1

When you grab the edge of the wheel with your hand and stop it from spinning, your force and its torque are internal. 

In the absence of external torque, the angular momentum remains conserved 

Initial angular momentum of wheel and merry-go-round is counterclockwise when observed from above. 

When wheel stops, the merry-go-round begins to rotate counterclockwise (as observed from above) 

The correct choice (b) It begins to rotate counterclockwise (as observed from above) 

Answer 2

Just like mass, energy, linear momentum, and electric charge, angular momentum is also conserved.

The wheel has angular momentum.  I don't remember whether it's
up or down (right-hand or left-hand rule), but it's consistent with
counterclockwise rotation as viewed from above.

When you grab the wheel and stop it from spinning (relative to you),
that angular momentum has to go somewhere.

As I see it, the angular momentum transfers through you as a temporary
axis of rotation, and eventually to the merry-go-round. Finally, all the mass
of (merry-go-round) + (you) + (wheel) is rotating around the big common
axis, counterclockwise as viewed from above, and with the magnitude
that was originally all concentrated in the wheel.