# Ball tied to string- centripetal force

1. Mar 26, 2009

### Dannystu

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

A ball, mass m = 1.5 kg is twirled at constant speed v at the end of a massless string in a vertical circle of radius r = 1.2 m. The period for this uniform circular motion is T = 1.3 s. Free body diagrams for the ball at the top and at the bottom of the circle are shown.
a. Compute the speed v of the ball.
b. Compute the ball’s centripetal acceleration.
c. Compute the “centripetal force” on the ball.
d. When the ball is at the top (point A in the figure) compute the tension FTA in the string.
e. When the ball is at the bottom (point B in the figure) compute the tension FTB in the string.

2. Relevant equations

I understand all the parts except for question c, is the formula for centripetal force m*(v^2/r)? Or is it the same as the The tension in the string?

2. Mar 26, 2009

### Staff: Mentor

Yes.
No, they are not the same.

3. Mar 26, 2009

### Dannystu

thanks a lot Doc!