Name the devices or machines which convert (1) Chemical Energy into Heat Energy (2) Light Energy into Heat Energy (3) Heat Energy into Kinetic Energy. What must be the power of the brakes of a car for them to stop the car moving at a velocity of 60 km per hour , weighing 1500 kg?

1) Matchstick converts chemical energy to heat energy.

2) Solar cookers convert light energy to heat energy.

3) Engines convert heat energy of the burnt fuel to kinetic energy of the vehicle.

=> 

Mass of the car (m) = 1500kg

Velocity of the car (v) = 60km/h =16.6667m/s

K.E. of the car = 0.5� m�v² = 0.5�1500�16.667²=208.33kJ

To stop the car, the brakes must provide energy of 208.33kJ.