According to Newtonian mechanics for a spherical mass distribution, what equation relates the orbital velocity ($v$) to the enclosed mass ($M(r)$) at radius ($r$)?
Answer
$v^2 = G M(r) / r$
This relationship is derived by equating the centripetal force with the gravitational force, resulting in the squared velocity being proportional to the enclosed mass divided by the radius, multiplied by the gravitational constant $G$.
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