Why is the answer to gravitational potential energy question C?

AI Thread Summary
The discussion centers on understanding why the answer to a gravitational potential energy question is C. A user seeks clarification on the calculation involving the gravitational potential energy of a cubical block, specifically considering the center of mass. They propose a formula, 3m*g*(3/2 l)=9/2mgl, to calculate the potential energy, attributing the height to the center of mass being at 3/2 l. The conversation emphasizes the importance of correctly identifying the center of mass in such calculations. Overall, the focus is on clarifying the reasoning behind the gravitational potential energy answer.
jack1234
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The answer is c, but I can't figure out what is the reason, can somebody kindly explain it?
http://tinyurl.com/32322t
 
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What do you think about gravitational potential energy of a cubical block?
 
I am thinking about centre mass...
So what I am figuring is
3m*g*(3/2 l)=9/2mgl...(3/2 l because the centre of mass is at that height)
Is it correct?
 
perfect.
 

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