A car is driven at an average speed of 100.0 km/hr for 2 hours, then at an average speed of 50.0 km/hr for the next hour. What was the average speed for the 3-hour trip?

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?