A hockey player skates across a pond with constant velocity v and hits a puck straight ahead toward the goal. We can assume there is no friction.
After the puck is hit, what is the velocity of the center of mass of the hockey player-puck system?

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?