Advertisements
Advertisements
प्रश्न
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.
उत्तर
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
संबंधित प्रश्न
A lamp consumes 1000 J of electrical energy in 10 s. What is its power?
An electric heater is rated 1500 W. How much energy does it use in 10 hours?
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)
Calculate the work done by the brakes of a car of mass 1000 kg when its speed is reduced from 20 m/s to 10 m/s?
An electric heater uses 600 kJ of electrical energy in 5 minutes. Calculate its power rating.
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 : work done by the car.
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 an experiment to measure his power, a student records the time taken by him in running up a flight of steps on a staircase. Use the following data to calculate the power of the student :
Number of steps = 28
Height of each step = 20 cm
Time taken = 5.4 s
Mass of student = 55 kg
Acceleration = 9.8 m s−2
due to gravity
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?
