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प्रश्न
Answer the following in a word or two or in a sentence.
Write the formula for calculating the efficiency of a machine.
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उत्तर
Efficiency =`"Output energy"/"Input energy"`
The percentage value of efficiency of a machine is calculated as
Efficiency =`" Output energy"/" Input energy"`× 100 %
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संबंधित प्रश्न
Write true or false of the following statement.
A gum bottle lying on a table has no energy.
Fill in the blank
The S.I.unit of energy is ______
Match the following columns
| COLUMN A | COLUMN B |
| 1. Running water | 1. heat energy |
| 2. Burning | 2. vibrations |
| 3.Energy | 3.atom bomb |
| 4.Sound energy | 4.kinetic energy |
| 5.Nuclear energy | 5.joule |
Answer the following in short.
What do you understand by the term efficiency of a machine’?
Name the quantity whose unit is :
(a) kilowatt
(b) kilowatt-hour
Derive the relation between commercial unit of energy (kWh) and SI unit of energy (joule).
- Take two aluminium channels of different lengths.
- Place the lower ends of the channels on the floor and hold their upper ends at the same height.
- Now take two balls of the same size and weight and release them from the top end of the channels. They will roll down and cover the same distance.
- At the moment of releasing the balls, which energy do the balls have?
- As the balls roll down which energy is converted into which other form of energy?
- Why do the balls cover the same distance on rolling down?
Note: The question is wrong. It should be "Why do the balls cover the same distance after rolling down"? - What is the form of the eventual total energy of the balls?
- Which law related to energy does the above activity demonstrate? Explain.
If the energy of a ball falling from a height of 10 metres is reduced by 40%, how high will it rebound?
We make useful objects from a variety of substances. Another use of substances is that we get energy from some of them.
There is a car. Its tank is full of fuel but it does not move. Why is that?
A ball is dropped from a height of 10 m. If the energy of the ball reduces by 40% after striking the ground, how much high can the ball bounce back? (g = 10 m s–2)
