✔ 最佳答案
對不起!
缺乏足夠資料而無法計算。
如果運用「newton's law of gravitation」,
F = G [(mass of 星球 * mass of 非常小的物體) / r^2]
F is gravitational force
G is universal gravitational constant
r is the distance between centres of both object
therefore ,地面上的重力加速(g) = G [mass of 星球 / (r+m)^2] ,
再用番 s = 0.5 (g)( t^2) ,
t ={ [2m(r+m)^2] / G(mass of 星球) }^0.5
參考: new way physics for advanced level -mechanics Mok Tim-ming , Wong Chi-san , Poh Liong-yong