What is the linear speed v of a unit mass located at the inner equator of such a sphere?

Electromagnetic induction. a coil of wire contains n turns and has an electrical resistance r. the radius of each turn is a. initially, inside the coil there exists a uniform magnetic field of magnitude b0 parallel to the axis of the coil. the magnetic field is then reduced slowly. the current induced in the coil is i. how long does it take for the magnitude of the uniform field to drop to zero?

Aboy with a mass 25 kg climbs into a small tree. he sits on a branch that is 2.o m above to the ground. what is his gravitational potential energy above the ground?

The electric potential a distance r from a small charge is proportional to what power of the distance from the charge? a. r^-1 b. r c. r^-2 d. r^2