# Homework Help: Rotational problem im stuck on

1. Feb 22, 2005

### cstryker02

A 500 g ball swings in a vertical circle at the end of a 1.5-m-long string. When the ball is at the bottom of the circle, the tension in the string is 15 N.

What is the speed of the ball at that point?

2. Feb 22, 2005

### faust9

what have you done so far? did you draw a fbd with the ball at the bottom of the circle? Did you sum the forces acting on the ball at that point? I'd say start there and see if you get an answer.

Good luck.

3. Feb 22, 2005

### cstryker02

yea i have done the FDB but im totally lost on the equations for the problem, i dont know how to find the speed with the "knowns" that i have been given.

4. Feb 22, 2005

### faust9

Well, you have 15N acting toward the center of the circular path and 4.905N acting down. Do you know of any pseudo-forces associated with circular motion? Do you know what force keeps a person stuck to the walls of one of those spinning amusement park rides, or the force you feel when a car goes around a corner?