Trent builds a model electric motor. when he connects a battery to the motor, the motor spins through a half rotation and stops. which is the most likely solution to the problem?

answer checking the commutator, because the current is not reversing

Aplayground merry-go-round has a radius of 4.6 m and a moment of inertia of 200 kg-m2 and turns with negligible friction about a vertical axle through its center. a child applies a 26.0 n force tangentially to the edge of the merry-go-round for 15.0 seconds. if the merry-go-round is initially at rest, how much work did the child do on the merry-go-round?