I just watched this http://www.youtube.com/watch?v=eVl5zs6Lqy0" video...(adsbygoogle = window.adsbygoogle || []).push({});

If W = KE ---> Fd = [mv^2] / 2

If in a spring, force is equal to a constant (k) times how far its been stretched (d), then subbing kd for F in the first equation...

Kd^2 = [mv^2]/2

Rearranging, E = kd^2

But in my textbook, it says that E = 1/2 [kd^2]

Where did the 1/2 come from? Even in the video, W = Fd, so from the graph, you times F by d, getting a SQUARE, not a triangle, but he says you times F by d, and divide by 2 since your looking at the area (triangle) underneath...

Any help?

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# Homework Help: Question on forces and energy

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