# Force that Maintains Circular Motion

1. Apr 9, 2010

### x0ji11y

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

A string with the length of 4.23 m can support a weight of 25 g. If you add a weight and spin the string horizontally above your head, it breaks upon reaching a tangential velocity of 5.1 m/s. What is the mass of the weight?

so... radius=4.23m, V(t)=5.1 m/s, and mass=unknown

2. Relevant equations

Angular Displacement = (arc length) / (radius)
Centripetal Force = (mass)(tangential velocity)(tangential velocity) / (radius)

3. The attempt at a solution

I'm not quite sure which equations pertain to solving this type of problem, but I don't know where to get started when you're not given the value of the centripetal force... Any help would be greatly appreciated! Thanks!

2. Apr 9, 2010

### Kabbotta

a = v^2/r, for centripetal motion.

Then use that acceleration value to relate the opposing forces. The tension in the string and the acceleration of the weight. A newton's second type equation. Solve for the mass. Total F = T - ma = 0