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I'm trying to work through an example of a equation where circular motion can be expressed . I'm having difficultly understanding where the next line in the equation comes from. I have shown them below. My goal is to express 'V' although currently i am a few steps away from this.

Line 1

mgr + 0.5m(2[itex]\sqrt{}rg[/itex])^{2}= 0.5mv^{2}

Line 2

gr + (2[itex]\sqrt{}rg[/itex])^{2}/ 2 = 0.5v^{2}

I can follow the equation such that i understand both 0.5m cancels out from both sides but i get lost when i try to figure out how i lose the m from the mgr expression in line 1 from line 2?

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# Equation re-arrangement

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