1. How much work is required to lift a 4kg object 3m high?
2. When a car stops, 60 000 J of work is done by the brakes
in a time of 6s. Calculate the power of the brakes.
3. A crane lifts a 90 kg mass a height of 12 m. Calculate the
gravitational potential energy gained by the mass. Use
g = 9.8 N/kg.
4. Determine the kinetic energy of a 750-kg roller coaster
car that is moving with a speed of 20.2 m/s.