Question

The moment, a force retards the motion of a body, what is the nature of work done by the force?
Give reason and list any 2 ex of such situation.

Answer 1

The moment when a force retards the motion of the body, the nature of work done is Negative, as the motion of the body is in opposite direction of the force exerted on it.
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Examples of negative work done are ;
1. Work done by the person to draw water from the well through pully.
2. Work done by frictional force.
3. Work done by gravitational Force when the object is thrown upward.
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Answer 2

the work done by the force is negative since the body moves in a direction opposite to the direction of the applied force.

here the angle between the direction of force and the displacement is 180°
So A = 180 ; cos A = -1
work done(W) = F S cos A = -FS
therefore
work done is negative
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EXAMPLES
1)a ball thrown upwards against the force of gravity.
2)walking on the ground . when a person walks on the ground he is doing negative work against the force of friction.