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WORK DONE & ENERGY Produced by Tsang Siu Chung. Work done In everyday language,work may mean anything that people do. In science,it is given a more precise.

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Presentation on theme: "WORK DONE & ENERGY Produced by Tsang Siu Chung. Work done In everyday language,work may mean anything that people do. In science,it is given a more precise."— Presentation transcript:

1 WORK DONE & ENERGY Produced by Tsang Siu Chung

2 Work done In everyday language,work may mean anything that people do. In science,it is given a more precise meaning: work is done whenever a force moves an object.

3 Work = force  distance moved in the direction of the force W = F s

4 s FF W = F s cos  s Work is measured by newton metre (N m) Joule ( J )  F  F

5 1 joule of work is done when a force of 1 newton moves a distance of 1 metre in the direction of the force. Important definition

6 Energy Things have energy if they can do work.We can think of energy as a capacity for doing work in the future. Energy,like work, is measured in joule(J). BOB!

7 Now,we will talking about the mechanical energy. The followings are different forms of mechanical energy. Kinetic energy Gravitational potential energy Strain energy

8 Kinetic energy A moving object has kinetic energy. The faster it moves the more energy it possesses. When a human run,chemical energy from the food changed into kinetic energy.

9 Gravitational potential energy When you lift a box up, it gains gravitational potential energy. The higher the box the more gravitational potential energy it possesses. If the box falls down, its gravitational energy is changed into kinetic energy. BOX Gain gravitational energy

10 Strain energy Another form of potential energy. It is energy possessed by an elastic object when it is stretched, compressed or bent. If the elastic is released, its strain energy is changed into the kinetic energy.

11 Energy change and work Work is done whenever energy is transferred from one from to another. Work done = Energy transferred Example: If a falling stone loses 10 joules of gravitation potential energy and gains 10 joules of kinetic energy, the gravitational force acting does 10 joules of work in accelerating the stone.

12 Energy in one form Energy in another form Work is done

13 This is the end of my project. I hope that you will have a general idea about Thank you. THE END


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