In an electric car, regenerative braking is used to recharge batteries.

The principle of regenerative braking involves converting the
kinetic energy of the vehicle into energy stored in a battery. If a
car is traveling at a speed of 30 km/h and is stopped completely
by braking, what would be the energy stored in the battery if the
mass of the car is 1000 kg and the energy conversion effi ciency is
assumed to be 100%? If this braking happens at a constant rate for
5 seconds, what is the average rate of power transfer?