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Question
In what way does an ‘Ideal machine’ differ from a ‘Practical machine’?
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Solution
Ideal machine has 100% efficiency i.e., work done on the machine = work done by the machine.
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P, Q and R are three forces which act as shown in fig.
The point O lies in the same plane. Given, P = Q = R = 10N
(i) Which force has the least moment about O? Give a reason.
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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 |
What is work?
State whether work is done or not, by writing yes or no, in the following case:
A man pushes a wall.
