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प्रश्न
Define the term energy.
उत्तर १
“Capacity of doing work” is called Energy.
उत्तर २
Energy, in physics, is the capacity for doing work. It may exist in potential, kinetic, thermal, electrical, chemical, nuclear, or other various forms. There are, moreover, heat and work-i.e., energy in the process of transfer from one body to another.
संबंधित प्रश्न
When do we say that work is done?
Define 1 J of work.
An object thrown at a certain angle to the ground moves in a curved path and falls back to the ground. The initial and the final points of the path of the object lie on the same horizontal line. What is the work done by the force of gravity on the object?
An electron emitter must have _____________ work function and ___________ melting point.
A coolie does no work against the force of gravity while carrying a luggage on a road.
Work is said to be done by a forte only when ................
The energy of a body is its capacity to do .........
The S.I. unit of work is
State the S.I. unit of work and define it.
.A man raises a box of mass 50kg to a height of 2m in 20s, while another man raises the same box to the same height in 50s. Compare:
(i) the work done, and
(ii) the power developed by them.
MULTIPLE CHOICE TYPE
In an electric cell which in use, the change in energy is from:
A vessel containing 50 kg of water is placed at a height 15 m above the ground. Assuming the gravitational potential energy at ground to be zero, what will be the gravitational potential energy of water in the vessel? (g = 10 m s-2)
What is the condition for a force to do work on a body?
If the work done by a force in moving an object through a distance of 20 cm is 24.2 J, what is the magnitude of the force?
When do we say that work is done? Write the formula for the work done by a body in moving up against gravity. Give the meaning of each symbol which occurs in it.
Ravi applied a force of 10 N and moved a book 30 cm in the direction of the force. How much was the work done by Ravi?
Name the force acting away from the centre of circular path.
What is the work done when the object acted upon by a force remains at rest?
A body does 20 J of work in 10 s. What is its power?
How fast should a boy weighting 30 kg run so that his kinetic energy is 375 joule?
A girl of mass 50 kg runs up a flight of 40 steps in 20 seconds. If each step in 20 cm high, calculate the power developed by the girl. (g= 10 ms-2).
Fill in the boxe to show the corresponding energy transformation.
Give an example
Electrical energy changes of sound energy.
An electric motor pump is 60% efficient and is rated 2.5 H.P. Calculate the maximum load it can lift through a height of 10m in 8 sec. (1 H.P. = 750 W).
Mention whether work is done or not in the following activity.
| S. No | Activity | Work done or not done |
| 1. | Pushing the door | |
| 2. | Holding a doll | |
| 3. | Sitting in a bus | |
| 4. | Pushing a wall | |
| 5. | Digging soil |
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
An engine is pulling a train.
State whether work is done or not, by writing yes or no, in the following case:
A man pushes a wall.
State whether work is done or not, by writing yes or no, in the following case:
A boy climbs up 20 stairs.
