# Homework Help: Uniform circle motion question

1. Oct 21, 2011

### shawli

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

A light string can support a stationary hanging load of 25.0kg before breaking. An object of mass m = 3.00kg attached to the string rotates on a frictionless, horizontal table in a circle of radius r = 0.800m, and the other end of the string is held fixed. What range of speeds can the object have before the string breaks?

2. Relevant equations

F = (m*v^2)/r

3. The attempt at a solution

I seem to only be able to solve this question in terms of F. As in, the max velocity can be:

v = (F*0.800/25)^0.5

Yet there is an actual numeric answer to this question.

I'm not sure what to do with the '3.0kg' given. Any hints would be appreciated!

2. Oct 21, 2011

### dacruick

when you spin this 3kg mass, there is a certain amount of tension in the string. The tension in the string cannot exceed 25kg * gravity. So what is the maximum speed you can spin a mass of 3kg so the tension in the string doesn't exceed 25kg * gravity?

3. Oct 21, 2011

### shawli

Ohh, this is the definition of "hanging load"? I understand now! Thank you.

4. Oct 21, 2011

### dacruick

You're very welcome