(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

http://img694.imageshack.us/img694/1115/pendulumcutquestion.jpg [Broken]

Please ignore the blue pen.

2. Relevant equations

E_{k}=1/2 mv^{2}

E_{p}=mgh

3. The attempt at a solution

Basically I looked at the problem firstly as the pendulum has reached the lowest point, therefore having an E_{p}of 0 and an E_{k}. Then I took a final point, where the string is cut. At this point there is E_{k}and E_{p}is there not?

The height would therefore be from the bottom of the swing, to the place where it's cut, which equals

6.4 - 6.4cos(30)

So now I have this

E_{k}= E_{k2}+ E_{p}

0.5mv^{2}= 0.5m(vsin30)_{2}+ mgh

Am I on the right track?

What do I do after this? I don't know what my next move should be...

Should I use the point where the string is cut , and set it equal to the ball at the top of the height's energy?

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# Homework Help: Hard Energy Physics Problem

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