Competitive divers pull their limbs in and curl up their bodies when they do somersaults. just before entering the water, they fully extend their limbs to enter straight down. how does their angular velocity change when they fully extend their limbs?

The angular velocity is reduced when the body is fully stretched.

Explanation:

Divers keep there bodies as compact as possible just to increase the angular velocity.

When they extend their limbs to enter straight down the angular momentum helps them to dive. The angular velocity is reduced when the body is fully stretched and diver's inertia is also not reduced. Thus a streamlined shape is formed which helps to penetrate more deeper into the water.

The impact area is reduced when fully stretched body is entered in to the water.

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it