Work and energy

Work and Energy Worksheet-7

51. Explain by an example that a body may possess energy even when it is not in motion.

52. Give two examples where a body possesses both, kinetic energy as well as potential energy.

53. How much is the mass of a man if he has to do 2500 joules of work in climbing a tree 5 m tall ?

(g = 10 m s-²)

54. If the work done by a force in moving an object through a distance of 20 cm is 24.2 J, what is the magnitude of the force?

Work and Energy Worksheet-8

71. A man X goes to the top of a building by a vertical spiral staircase. Another man Y of the same mass goes to the top of the same building by a slanting ladder. Which of the two does more work against gravity and why ?

72. When a ball is thrown inside a moving bus, does its kinetic energy depend on the speed of the bus ? Explain.

73. A bullet of mass 15 g has a speed of 400 m/s. What is its kinetic energy ? If the bullet strikes a thick target and is brought to rest in 2 cm, calculate the average net force acting on the bullet. What happens to the kinetic energy originally in the bullet ?

74. Name the commercial unit of measurement of energy.

75. Define kilowatt-hour.

Work and Energy Worksheet-9

1. The power output of an engine is 3 kW. How much work does the engine do in 20 s ?

2. An electric heater uses 600 kj of electrical energy in 5 minutes. Calculate its power rating.

3. Five electric fans of 120 watts each are used for 4 hours. Calculate the electrical energy consumed in kilowatt-hours.

4. Describe the energy changes which take place in a radio.

5. Write the energy transformations which take place in an electric bulb (or electric lamp).

6. Name five appliances or machines which use an electric motor.