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Under what conditions is the work done called positive,negative and zero work?Give ONE...

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tubee | Student, Grade 10 | (Level 1) Salutatorian

Posted April 16, 2013 at 7:12 PM via web

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Under what conditions is the work done called positive,negative and zero work?Give ONE example each of positive and negitive work.

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pramodpandey | College Teacher | (Level 3) Valedictorian

Posted April 17, 2013 at 8:14 AM (Answer #1)

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Work done W depends on two factors

1. Applied Force

2. Displacement

Since Displacement is vector quantity . So it depends on dirction and magnitude.

Mathematically we can define

`W=FScos(theta)`

where F is force , S is displacement and `theta`  angle or direction.

If `theta=0` ie. force applied and object displaced in direction of force.

work done is positive and maximum. e. g. Pushing an object

If `theta=90^o`  ,body displaced in perpendicular direction of force

work done is zero. Carry load doing work against gravity but displacement is perpendicular.

If `theta=180^o`

work done is negative. body displace in direction opposite to force.

Rowing boat.

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