I can't understand why there is no work done by an object moving in a circle?

Question

is it because there is no displacement? And why did there is a change in linear momentum? Is it because the velocity is changing?

Answer 1

there is

Answer 2

work done is a measure of force x displacement - if there is no  force or no displacement there is no work done.  

If you think of an object in orbit the force is acting towards the earth but all displacement is at right angles - so even though there is a force the displacement due to the force = 0 and so no work done.

Yes since velocity is changing - linear momentum is changing.

Answer 3

1) exactly, work is force x distance. As no distance is covered no work is done.

2) Linear momentum includes a vector component in addition to the mass and velocity  components of momentum. Since this vector is in the direction of motion and tangential to the circle the direction of the vector is constantly changing and so does the linear momentum.

Answer 4

work done= force x displacement - when u rotate an object theres no displacement.it means displacement=0.

therefore workdone=0.

velocity is changing ,it becomes acceleration.therefore work is done.- linear momentum is changing.

its a bit difficult to believe that.since we actually apply force when rotatin a stone tied to a thread....:-)

Answer 5

Work = force × displacement in the direction of the force

= |F|.|d|.cosθ

Since the force is always towards the centre of the circle and the displacement is always along the tangent θ=90° at all times.

W = |F|.|d|cos90° = |F|.|d|×0 = 0

The work done is 0.