How to prove this connection

1. Nov 9, 2008

blayman5

1. The problem statement, all variables and given/known data
I have to prove in a conservation of energy question

T-W =(mv^2)/L

mgL(1-cosO)=(mv^2)/2

mg=W

T=W(3-2Cos0)

How could I go about starting this?

2. Nov 9, 2008

asleight

Well, you can do this:

$$\vec{T} = \vec{W} + m\vec{v}^2/\vec{L} = m\vec{g} + m\vec{g}\vec{L}(1-\cos\theta) = \vec{W}\vec{L}(1-\cos\theta)$$. I'll leave the conclusion up to you to resolve.