A braking system loses 25% of its energy consumed in useful energy. What is its energy efficiency?

How much force must a locomotive exert on a 12840-kg boxcar to make it accelerate forward at 0.490 m/s2?

An artificial satellite circles the earth in a circular orbit at a location where the acceleration due to gravity is 6.03 m/s^2. determine the orbital period of the satellite.

Since the energy was not raising the temperature of the water during these segments, what was the energy used to do instead? your answer must include an explanation of what is happening to the molecules.