# Centripetal Net Force

1. Nov 20, 2008

### keemosabi

1. The problem statement, all variables and given/known data
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?

2. Relevant equations

3. 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 in to play?

2. Nov 20, 2008

### twotaileddemon

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

3. Nov 20, 2008

### keemosabi

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?

4. Nov 20, 2008

### twotaileddemon

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

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

5. Nov 20, 2008

### PhanthomJay

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

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