3. 1 a.
i) A rower rowing a boat:
The work done to overcome friction is transferred as energy to the thermal energy stores
of the water, oar and boat and to the surroundings.
ii) An electric motor to raise a car park barrier:
Energy is transferred by the current in the cables to increase the thermal energy stores
of the motor and the barrier mechanism and to the surroundings.
1 b.
Work done = F s
Work done = N x 50m
Work done = 150,000 J

4. 2a.
The thermal energy store of the brake pads increases.
The Kinetic energy store of the car decreases.
2b.
Work done = F s
Work done = N x 20m
Work done = 140,000 J

5. 3a i)
Work done = F s 3b
Work done = F s
Work done = 20 N x m
Work done = F s
Work done = 96 J
1400 J = F
7.0 m
3a ii)
Work done = F s
200 N = F
Work done = 80 N x m
Work done = 96 J

6. 3a i)
Work done = F s
Work done = 25 N x 12 m
Work done = 300 J
3b The chemical energy store of the student decreases.
The work done to overcome friction is transferred as energy to the thermal energy stores
of the box, the floor surface and to the surroundings.