Stan is speeding in a silver sedan at 77 m/s when he suddenly sees a stopped police car 90 m in front of him. He immediately applies the brakes and slows to 38 m/s by the time he is next to the police car. Find: (a) the acceleration, (b) how much time elapses?

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?