calculate the average force (in N) a 70.0 kg sprinter exerts backward on the track to accelerate from 2.00 to 8.50 m/s in a distance of 25.0 m, if he encounters a headwind that exerts an average force of 30.0 N against him.

Agas expands from an initial volume of 0.040 m^3 and an initial pressure of 210 kpa to a final volume of 0.065 m^3 while its temperature is kept constant. how much work is done by the system?

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.

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?