Efficiency

A motor takes 300 J to do 150 J work. Its effeciciency is:
1. 30 %
2. 50 %
3. 100 %
4. 200 %
Lubricants increase the efficiency of a car engine because:
1. they reduce friction.
2. they add extra energy to the fuel.
3. they are cheap.
4. they can be made from renewable resources.
Which one of these statements is correct about a perpetual motion machine?
1. It is 100 % efficient.
2. It cannot be more than 150 % efficient.
3. It needs no battery.
4. There is no such thing. Toys sold as perpetual motion machines actually have a battery.
If a machine is 10 % efficient, it means that:
1. It is a perpetual motion machine.
2. 10 % of the energy goes to waste.
3. 90 % of the energy goes to waste.
4. It will not operate at all.
A 60 watt light bulb is 2 % efficient. The amount of power turned into heat is:
1. 0 watts
2. 1.2 watts
3. 58.8 watts
4. 60 watts