why we take work done =0 in circular motion

why we take work done =0 in circular motion


4 Answers

Chetan Mandayam Nayakar
312 Points
11 years ago

Dear Akhil,

Work done≡∫F·ds (where F is force, and ds is infinitesimal displacement)

in circular motion F is always perpendicular to ds

therefore, F.ds≡zero. Therefore work done=zero

Please feel free to post as many doubts on our discussion forum as you can. If you find any question
Difficult to understand - post it here and we will get you the answer and detailed solution very quickly. We
are all IITians and here to help you in your IIT JEE preparation.

All the best Akhil !!!



Askiitians Experts

Chetan Mandayam Nayakar


Akshith Yeso
41 Points
11 years ago

Work done by a conservative forces in a closed loop is zero . Since centrifugal and centripetal forces are conservative, work done in circular motion is zero .If any non-conservative force like friction is present work done is not zero

Menka Malguri
39 Points
11 years ago

Conceptually,work done=force applied.displacement in the direction of force

When a particle moves in circular motion,two forces act on it,the tangential force and the centripetal force.

The centripetal force acts along the line joining the particle and the center of the circular path,but the particle is not diplaced in this direction due to the equal n opposite centrifugal applied on it and thus there is no displacement,hence no work done.

In case of tangential force,the direction of this force always keeps on changing as the direction of motion of the particle changes continuously.If we take any particular point on the circular path,the foce acts on the particle at that point in one direction and after taking a turn ,when the particle reaches the same point,the same force is applied but the displacement is zero,hence the work done is zero.

This can be applied for each n every point of the circular path n hence the work done at each n every point of the circular path is zero.

Ashwin Muralidharan IIT Madras
290 Points
11 years ago

Hi Akhil,


We don't take it to be zero.


If you see W = (F vector)dot(Displacement vector).

At any instant in time, F is towards the centre, and the displacement is along the tangent to the circle.

And hence these two vectors are perpendicular. (So sot roduct is zero).


And hence W = 0.


Best Regards,

Ashwin (IIT Madras).

Think You Can Provide A Better Answer ?