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  • A body is being raised to a height h from the surface of earth. What is the sign of work done by (a) applied force

A body is being raised to a height h from the surface of earth. What is the sign of work done by
(a) applied force
(b) gravitational force?

Answers (1)

When a body is raised to a height h, the force is applied in this case in the direction of displacement of the object.

a) so, the sign of the work done by the force is positive here

work done = \overrightarrow{F}d\overrightarrow{s }=Fds \cos \theta

As Fds is positive, \theta =0

b) the force of gravity always acts in the downward direction. However, the force in our case is being applied in an upward manner. So, the value of \theta =180

work done = \overrightarrow{F}d\overrightarrow{s }=Fds \cos 180=-Fds. Hence, here the sign is negative.

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infoexpert24

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