Advertisements
Advertisements
Question
A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not? Justify your answer.
Advertisements
Solution
Work is done whenever the given two conditions are satisfied:
- A force acts on the body.
- There is a body displacement by applying force in or opposite to the direction of force.
- A person holding a bundle of hay on his head becomes exhausted due to muscular weariness. This tiredness is caused by converting chemical energy into heat energy via muscular effort. The guy has done no work because his exertion does not cause the bundle over his head to move, i.e., s = 0.
APPEARS IN
RELATED QUESTIONS
A battery lights a bulb. Describe the energy changes involved in the process.
What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.
Find the energy in joules consumed in 10 hours by four devices of power 500 W each.
A load of 100 kg is pulled up by 5 m. Calculate the work done. (g = 9.8 m/s2)
A body of mass 100 kg is lifted up by 10 m. Find :
(i) the amount of work done
(ii) potential energy of the body at that height (value of g = 10 m/s2)
Fill in the blank with suitable word :
Power is the rate of doing ___________.
The power output of an engine is 3kW. How much work does the engine do in 20 s?
A car of weight 20000 N climbs up a hill at a steady speed of 8 m/s, gaining a height of 120 m is 100 s. Calculate : power of engine of car.
In loading a truck, a man lifts boxes of 100 N each through a height of 1.5 m.
How much work does he do in lifting one box?
In loading a truck, a man lifts boxes of 100 N each through a height of 1.5 m.
How much energy is transferred when one box is lifted?
