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$($a$)$ Evaluate the gravitational potential energy between two $5$ kg spherical steel

balls separated by a center$-$to$-$center distance of $16$ cm$.$

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$($b$)$ Assume the balls are both initially at rest relative to each other in deep space

$($when separated at the distance in part A$),$ and they then drift towards one other

until they collide. Use conservation of energy to find how fast will they be

traveling upon impact. Each sphere has a radius of $4\mathrm{.}1$ cm$.$

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