[填空题]
Two masses of $6.2\times10^3\,kg$ and $4.0\times10^3\,kg$ are initially separated by a distance of 4.3 m between their centers.
1.Calculate the gravitational potential energy of the two masses when in this arrangement. $E_g$ = $\times10^{-4}\,J$
2.Explain why your answer to part (a) is negative.
3.With reference to the gravitational potential due to the $6.2\times10^3\,kg$ mass, suggest how the gravitational potential energy would change if the $4.0\times10^3\,kg$ mass were moved further away.
