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

The gravitational self potential energy of a solid energy of a solid ball of mass density p and radius R is E. What is the gravitational self potential energy of a ball of mass density p and radius 2R?

2. Relevant equations

3. The attempt at a solution

The gravitational potential energy is given by the equation "mgh=U" where the mass relevant is the center of mass. Since it is a sphere with uniform density, the CM is in the center. This puts the CM of the first ball R above the ground and the second ball 2R above the ground. As for mass the second ball is heavier. Mass2/mass1= ((4/3 pi (r) cubed) p)/((4/3 pi (2 R) cubed) p) which tells me that ball 2 is 8 times heavier. Since g does not change the U of the second ball should be 8 times 2 which is 16 E. However the answer is 32 E. This question is hard. ahah Thanks!!!!! =)

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# Homework Help: Gravitational Potential Energy!

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