# Homework Help: A General Question About Fc

1. Oct 27, 2012

### student34

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

When an object travels in a horizontal circular motion attached to a string, it is understood that there is a force on the object directed towards the center. What force is acting on it to stop it from moving to the center?

2. Relevant equations

Fc = (mv^2)/r

3. The attempt at a solution

I know T gets used a lot with these equations, so I am going to guess tension. But, even if this is right, I do not understand where this tension is coming from or how it counter balances the centripetal force.

2. Oct 27, 2012

### Staff: Mentor

This is a bit of an ambiguous question. Your instructor might be looking for either of two plausible answers, or he might be trying to get you to think about why there are two plausible answers. But this being physicsforum, you're going to be steered in the "think about" direction....

The two plausible answers are "centrifugal force" and "there isn't any such force". Both answers will lead to correct and non-conflicting explanations of what's going on.

One last hint: The tension provides the centripetal force, so it is certainly not the tension that's stopping the object from moving in towards the center; on the contrary, it's the tension that's pulling the object towards the center.

3. Oct 27, 2012

### PeterO

But it does move towards the centre! But does not any closer.

without the string, the object would move in a straight line - a tangent to the circle it is actually following.
If you drew a diagram showing the circular path, and the tangential path, you will see that with the tangential path would have the object further from the centre.
by following the circular path the object is closer to the the centre than it would have been, rather than closer to the centre than it already is.

4. Oct 28, 2012

### student34

I get it, thank-you so much!