1. A pebble is dropped from the top of a cliff 60 m in height. The kinetic energy of the pebble equals twice its potential energy at a distance of _______ above sea level.   30 m   45 m   15 m   20 m   Hint Half-n-half Clue   2. The SI unit of power is   Joule   Volt   Watt   Half-n-half Clue   3. A boy throws a ball vertically upwards from ground level. If the ball reaches a maximum height of 250 m and the gravitational acceleration is 9.8 m/s2, with what speed did the boy throw the ball?   35 m/s   70 m/s   50 m/s   10 m/s   Half-n-half Clue   4. The maximum amount of work that can be done by a 70 kW machine in 11 seconds is   6 J   770 J   6 kJ   770 kJ   Half-n-half Clue   5. 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   6. Both work and heat are measured in Joules.   True   False   7. Power is the rate of doing work.   True   False