# The mass of the ball is m, and the length of the string is L

1. Jan 16, 2012

### rbwang1225

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

A man plays a Yo-Yo ball as shown in the figure. The mass of the ball is m, and the length of the string is L. The ball moves in a circle along a vertical plane. What is the difference of the string tension at the lowest point ($(T_{2})$) and the highest point ($(T_{1})$)

3. The attempt at a solution

($\frac{mv^{2}}r=T_1+mg=T_2-mg$)
$\Rightarrow T_2-T_1=2mg$
But the answer is 6mg, I guess the problem is that v is not equal at the two different positions. In this case, I don't know how to solve it.

2. Jan 16, 2012

Re: tension