# The work done by the force of friction on a body sliding on a rough horizontal surface will be-

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The work done by the force of friction on a body sliding on a rough horizontal surface will be-
1. Positive
2. Negative
3. Zero
4. Constant

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Correct Answer - Option 2 : Negative

The correct answer is option 2) i.e. Negative.

CONCEPT:

• Work done by a force: Work is said to be done by a force on a body when there is a displacement of the body due to that force.

The magnitude of work done is given as:

W = F.S.Cosθ

where, W = Magnitude of work done by the force(F) in joule, F = Magnitude of force, in newton, SCosθ  = Component of the Displacement in the direction of the force, in meter

• Positive and negative work: When the force and the displacement are in the same direction, work done is positive.
• When the force and displacement are in opposite direction, work done is negative.
• Zero work done: Work done is zero if force and displacement are perpendicular to each other or if the displacement of the body is zero.

EXPLANATION:

• When a body is sliding on a rough horizontal surface, the force of friction acts in the direction opposite to the direction of motion.
• Hence, force and displacement are in opposite direction.
• Therefore, work done by the force of friction on a body sliding on a rough surface is negative.

• If the force and displacement are in the same direction, the work done is positive.
• If force and displacement are perpendicular to each other, the work done is zero.
• A constant work done happens when neither the magnitude nor the direction of either force or displacement is changing.