Understanding Centripetal Net Force in Circular Motion

[keemosabi]

Homework Statement

If you swing a ball in a horizontal circle around your head, what is the direction and magnitude of the net force acting on the ball?

Homework Equations

The Attempt at a Solution

I said none because the ball is moving at a constant velocity. Is this correct? Or does the centripetal force come into play?

 

[twotaileddemon]

The direction of the force is inward, perpendicular to the velocity at any given moment of time.

 

[keemosabi]

The direction of the force is inward, perpendicular to the velocity at any given moment of time.

Is it a net force? If it were, wouldn't the ball be accelerating inward? Doesn't that force just offset the ball pulling on the string?

 

[twotaileddemon]

good point.. I didn't see that "net" there.

In that case, I do believe the -net- force is zero, as you said.

 

[PhanthomJay]

Is it a net force?

yes

If it were, wouldn't the ball be accelerating inward?

yes, it is , in the inward centripetal x direction.

Doesn't that force just offset the ball pulling on the string?

No, that's Newton's 3rd law, the string pulls on the ball, and the ball pulls on the string, with a force equal in magnitude and opposite in direction, always.