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http://img8.imageshack.us/img8/9198/workdone.jpg [Broken]

The first part of this problem is OK but I'm asking about the second part

We know that the work done is F *d*cosine the angle between the force direction and

the displacement direction .So why the book calculated the work done in this way?

I know that the work done in this case is the potential energy which is (m*g*d) and this does works!! But my problem is why the book calculated the work done in this way?

Another way :

Its given that the angle between force direction and the displacement direction is 60 then the result is the same.

So Are all of these ways right?

I hope you can understand my problem

Thanks so much

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# Homework Help: A Physics problem

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