1. The energy losses from machines are mostly dissipated as sound energy.   True   False   2. A machine that produces 60 J of work by using 80 J of energy has an efficiency of   75 %   20 J   25 %   15 J   Hint Half-n-half Clue   3. Kinetic energy of a body in motion equals the product of half its mass and the square of its _______   distance   velocity   acceleration   Half-n-half Clue   4. The maximum amount of work that can be done by a 60 kW machine in 10 seconds is   6 J   600 J   6 kJ   600 kJ   Half-n-half Clue   5. A mass of 4 kg is raised through a vertical distance of 100 m. If the gravitational acceleration is 9.8 m s-2, then the potential energy gained by the mass is   3920 J   39.2 J   980 J   400 J   Half-n-half Clue   6. Both work and heat are measured in Joules.   True   False   7. A body loses 7840 J of potential energy in falling through 100 m. If the gravitational acceleration is 9.8 m s-2, then the body has a mass of   78 kg   980 kg   800 kg   8 kg   Half-n-half Clue