Advertisements
Advertisements
प्रश्न
No work is done by a man moving on a horizontal road while carrying a box on his head. Explain.
Advertisements
उत्तर
The displacement of the man and box is along the horizontal direction. Thus, the angle between the displacement and the force of gravity is 900;
Thus, W = Fd cos 900 = 0
Hence, no work is done against gravity in this case; however some work is done against friction.
APPEARS IN
संबंधित प्रश्न
Power spent by a body depends on the time for which it does work.
A boy of mass 40 kg climbs up the stairs and reaches the roof at a height 8 m in 5 s. Calculate:
- the force of gravity acting on the boy,
- the work done by him against the force of gravity,
- the power spent by boy. (Take g = 10 m s-2)
How much work is done when a body of mass m is raised to a height h above the ground?
Write the formula for the work done on a body when a force acts on the body in the direction of its displacement. Give the meaning of each symbol which occurs in the formula.
A body does 20 J of work in 10 s. What is its power?
A block of mass 30 kg is pulled up a slope, as shown in diagram with a constant speed, by applying a force of 200 N parallel to slope.
A and B are initial and final positions of block.
(i) Calculate the work done by force in moving the block from A to B.
(ii) Calculate P.E. gained by block. [g=10ms-2]
An electric motor of power 100 W is used to drive the stirrer in a water bath. If 50% of the energy supplied to the motor is spent in stirring the water. Calculate the work done on the water in one minute.
A bucketful of water is to be drawn from a well ______ will be done when a ______ is applied to do this because there will be a ______ of water.
(displacement, work, force)
