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| SI Unit of Work |
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| W = F x S |
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| SI unit of F is N and that of S is m [N = newton] |
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| 1N m is defined as 1 joule. |
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| i.e., 1 joule = 1 N m |
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| One joule is the work done when the point of application of a force of one newton moves through a distance of one metre in the direction of force. |
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| 1 N m is referred as joule after the British Scientist James Prescott Joule. |
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| The letter 'J' denotes Joule. |
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| Higher units of work are kilojoule and megajoule. |
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| 01. An object of mass 5 kg is lifted up through a distance of 2 metre. What is the work done? |
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| Solution: |
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| W = F x S |
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| Force acting on the object is given by F = mg [Newton's second law of motion] |
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| Mass of the object (m) = 5 kg |
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| Distance moved = 2m |
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| Therefore, Work done = F x S |
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| = 98 J |
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| 02. How much work is done, when a force of 25 N displaces an object through 10 m, in the direction of the force applied? |
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| Solution: |
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| Force (F) = 25 N |
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| Distance moved (S) = 10 m |
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| Work done (W) = F x S |
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| 03. A work of 250 J is done when a force of 10 N is applied on an object. Calculate the distance through which the object moves. |
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| Solution: |
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| Work done (W) = 250 J |
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| Force applied (F) = 10 N |
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| Distance (S) = ? |
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| W = F x S |
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| Distance covered = 25 m |
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