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Work, Power and Energy 1. Work : Work is said to be done, when a force or a component of a force causes displacement in its own direction. 2. Erg : When a force of one dyne, causes a displacement of 1 cm, in its own direction, the work done is said to be of one erg. It is a CGS unit of work. 3. Joule : When a force of one newton, causes a displacement of 1 m, in its own direction, the work done is said to be of one joule. It is a SI unit of work. 4. Relation between joule and erg : 1 J = (1 N) (1 m) = (105 dyne) (100 cm) = (107 dyne cm) = 107 ergs. 5. Bigger units of work : 1 kilojoule (kJ) = 103 J; 1 megajoule (M.J.) = 106 J; 1 gigajoule = 109 J 6. Power : The rate of doing work is called power. or The product of force and velocity is called power. 7. Watt (J/s) : When a work of 1 J is done in one second, the power is said to be of one watt. It is the SI unit of power. Class-X 1 Key points
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