Astronomers believe that cosmic background radiation formed:
a. about 1 billion years ago.
b. about 1 million years ago.
c. shortly after the big bang.
d. about 100,000 years ago.

Aperson stands on a platform, initially at rest, that can rotate freely without friction. the moment of inertia of the person plus the platform is ip. the person holds a spinning bicycle wheel with its axis horizontal. the wheel has moment of inertia iw and angular velocity ωw. take the ωw direction counterclockwise when viewed from above. part a what will be the angular velocity ωp of the platform if the person moves the axis of the wheel so that it points vertically upward?