# Centripetal Acceleration definition help

1. Jul 9, 2013

### oneplusone

Hello, my textbook says that the magnitude
of centripetal acceleration is equal to the sum of the forces acting on that object.
(this is in regard to an object in a circular path, by a string. See https://upload.wikimedia.org/wikipedia/commons/thumb/c/c9/Centripetal_force_diagram.svg/220px-Centripetal_force_diagram.svg.png for an example)

I was wondering why is this so? To me, it doesn't make sense that they are equal in magnitude, since the forces are perpendicular.

2. Jul 9, 2013

### rcgldr

Only the sum of forces component that is perpendicular to the path of an object results in centripetal acceleration. The sum of forces component in the direction of the path of an object results in tangental acceleration.

3. Jul 9, 2013

### oneplusone

So could you please briefly describe how will you solve for Tension? generically?

4. Jul 9, 2013

### rcgldr

The link to the diagram isn't working for me. In what direction is the string rotating, horizontally or vertically or .... ?

5. Jul 10, 2013

### oneplusone

Try here.

6. Jul 10, 2013

### rcgldr

Looking at that diagram, there are no other forces acting on the mass other than centripetal force, which equals m v^2 / r or m ω^2 r. The centripetal acceleration would be v^2 / r or ω^2 r.