ICSE.X.PHYSICS. 2. WORK, POWER AND ENERGY

12. The power rating of a machine is 2 kW. How much work does the machine do in 10 seconds?

• 10 kJ

• 20 kJ

• 30 kJ

• 40 kJ

13. A washing machine consumes 400 kJ of electrical energy in 4 minutes. Calculate its power rating.

• 1000 W

• 1500 W

• 1666.66 W

• 2000 W

14. A truck of weight 40000 N climbs up a hill at a uniform speed of 5 m/s and gains a height of 50 m in 80 seconds. Calculate: (a) work done by the truck. (b) power of the engine of the car. Ans. (a) 20000 kJ (b) 2500 kW

• (a) 20000 kJ (b) 2500 kW

• (a) 15000 kJ (b) 2000 kW

• (a) 25000 kJ (b) 3000 kW

• (a) 18000 kJ (b) 2200 kW

A crane lifts a load of 500 kg to a height of 10 metres in 5 seconds. Calculate the power of the crane.

• 5 kW

• 10 kW

• 15 kW

• 20 kW

16. Ten electric fans of 75 watts each are used for 2 hours. Calculate the electrical energy consumed in kWh.

• 1.5 kWh

• 2.0 kWh

• 1.0 kWh

• 2.5 kWh

The work done on a body depends on the:

• mass of the body

• acceleration produced in the body

• distance moved by the body

• all of these

The work done by frictional force on a moving body is

• positive

• zero

• negative

• none of these

When a satellite moves in its orbit around the Earth:

• no work is done

• positive work is done

• negative work is done

• a huge amount of work is done

An engine pulls a train on tracks. Work is done here:

• by the train on the engine

• by the engine on the train

• by the engine on the tracks

• none of these

When a man pushes against a wall and the wall does not move; the energy consumed is due to work done:

• by the man on the wall

• by the man on the ground

• by the man on his own body

• none of these