1. A mass of 11 kg is raised through a vertical distance of 30 m. If the gravitational acceleration is 9.8 m s-2, then the potential energy gained by the mass is   330 J   3234 J   294 J   108 J   Hint Half-n-half Clue   2. If an engine does 679 J of work in 7 seconds, its average power is   686 W   97 W   672 W   4753 W   Half-n-half Clue   3. Efficiency of a machine equals   Work Input / (Work Input + Work Output) × 100 %   Work Output / Work Input × 100 %   Work Output / (Work Input + Work Output) × 100 %   Work Input / Work Output × 100 %   Half-n-half Clue   4. The SI unit of power is   Volt   Watt   Joule   Half-n-half Clue   5. If there is no friction, the efficiency of a machine can be greater than 100 %.   True   False   6. The maximum amount of work that can be done by a 20 kW machine in 12 seconds is   2 J   240 J   2 kJ   240 kJ   Half-n-half Clue   7. A body loses 2744 J of potential energy in falling through 40 m. If the gravitational acceleration is 9.8 m s-2, then the body has a mass of   392 kg   280 kg   7 kg   69 kg   Half-n-half Clue