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The work done is zero when the force is acting perpendicular to the fsurface .this is becacuse cos90 is =0 .My question is why are we taking cos 90 here.

The work done is zero when the force is acting perpendicular to the fsurface .this is becacuse cos90 is =0 .My question is why are we taking cos 90 here.

Grade:10

1 Answers

Raheema Javed
156 Points
7 years ago
In this case the work done is the dot product force and distance,
F·ds = Fcosθds
where θ is the angle between the force vector and the direction of movement
In the notable case of a force applied to a body always at an angle of 90 degrees from the velocity vector (as when a body moves in a circle under a central force), no work is done at all, since the cosine of 90 degrees is zero.

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