Physics

Problem

A planet may be treated as a uniform solid sphere of radius

R

and mean density

\rho

. a. Derive an expression for

\rho

in terms of

g

G

and

R

. (Symbols have their usual meaning.) b. Using

g = 9.8\,\text{m s}^{-2}

R = 6.37\times10^{6}\,\text{m}

and

G = 6.67\times10^{-11}\,\text{N m}^{2}\text{kg}^{-2}

, calculate the mean density of Earth.