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प्रश्न
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संबंधित प्रश्न
Define 1 J of work.
Can there be displacement of an object in the absence of any force acting on it? Think. Discuss this question with your friends and teacher.
Power spent by a body depends on the time for which it does work.
Define 1 joule of energy.
Give reasons for the following A teacher moving around in the class is doing work but a child standing and reading a book is not doing any work.
When is work said to be done by a force?
Fill in the blank with suitable word :
1 joule is the work done when a force of 1 __________ moves an object through a distance of one __________ in the direction of __________.
How much work is done when a force of 2 N moves a body through a distance of 10 cm in the direction of force?
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?
Distinguish between work and power.
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?
(a) Define power and name its unit.
(b) A girl weighting 50 kg climbs up 60 steps each of 20 cm height in 5 minutes. Calculate the power developed.
State the energy changes which take place when Water stored in the dam is used to turn turbine in dynamo.
Can two agents, doing the same work, have different power?
What are the advantages and disadvantages of using solar cells for producing electricity?
A girl of mass 40 kg runs a height of 80 stairs, each 25 cm high with a load of 20 kg on her head in 25 sec. If g is 10 m/s2, find:
(i) Gravitational force acting on the girl.
(ii) Work done by her.
(iii) Useful work done by her.
(iv) Her power in watt.
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’.
Food grains are getting dried in the sun.
