STANDARD Physics Work Done by a Constant Force MCQ Question
A body is being raised to a height h from the surface of earth. What is the sign of work done by applied force and gravitational force respectively?
Positive, Positive
Positive, Negative
Negative, Positive
Negative, Negative
Correct Answer
Detailed Explanation
Work done, W = F·d = Fdcosθ, where θ is the angle between the force F and displacement d. As the body moves along the direction of applied force, θ = 0°, W = Fdcos0° = Fd. It is positive. As the body moves in a direction opposite to the gravitational force which acts vertically downwards, θ = 180°, W = Fdcos180° = -Fd. It is negative.
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