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प्रश्न
What should be the characteristic of a source of energy?
उत्तर
A good source of energy should have the following characteristics:
(i) It should do a large amount of work per unit mass or volume.
(ii) It should have a high calorific value.
(iii) It should be easily accessible over a long period of time.
(iv) It should be economical and easy to store and transport.
(v) It should be safe and convenient to use.
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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)
A machine raises a load of 750 N through a height of 16 m in 5 s. calculate:
- energy spent by machine,
- power at which the machine works.
The work done by a force acting obliquely is given by the formula : W = F cos θ ✕ s. What will happen to the work done if angle θ between the direction of force and motion of the body is increased gradually? Will it increase, decrease or remain constant.
Choose one or more correct alternatives.
For work to be performed, energy must be ______.
- transferred from one place to another
- concentrated
- transformed from one type to another
- destroyed
A uniform circular motion is an accelerated motion. Justify it.
What is the SI unit of work?
What do you mean by a kilo joule?
Distinguish between work and power.
Complete the following sentences:
Kilowatt is the unit of ....... and kWh is the unit of
A boy of mass m climbs up a staircase of vertical height h.
- What is the work done by the boy against the force of gravity?
- What would have been the work done if he uses a lift in climbing the same vertical height?
Can work done be zero even if force acts on the body?
An object is dropped from a height H. when is its
(i) P.E. maximum,
(ii) K.E. maximum,
(iii) P.E. = K.E.?
A body does 20 J of work in 10 s. What is its power?
State the amount of work done by an object when it moves in a circular path for one complete rotation. Give a reason to justify your answer.
State whether work is done or not, by writing yes or no, in the following case:
A man pushes a wall.
