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Sound — Science STD 9 — Question

Gujarat BoardEnglish MediumSTD 9ScienceSound2 Marks
Question
When is the work done said to be negative$?$
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Answer

When displacement of the body is in direction opposite to direction of force.
Example: when a person lifts a weight then the displacement of the body is in direction opposite to Gravitational Force and thus it can be said that the work done on the body by gravity is $NEGATIVE ($angle between Gravitational Force and Displacement is $180$ degree and cos $180 = -1).$

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