Ответ:
ВРоде так)
T=240 мин = 240*60 сек
f=1/T
w=2*pi*f = 2*pi / T
a=w^2*(Rз+h) = GM/(Rз+h)^2 = GM/Rз^2 *Rз^2/(Rз+h)^2 = g*Rз^2/(Rз+h)^2
w^2*(Rз+h) =g*Rз^2/(Rз+h)^2
(Rз+h)^3 = g*Rз^2/w^2
(Rз+h) = (g*Rз^2/w^2)^(1/3)
h= (g*Rз^2/w^2)^(1/3) — Rз = (g*Rз^2/(2*pi/T)^2)^(1/3) — Rз = (9,81*6370000^2/(2*pi/(240*60))^2)^(1/3) — 6370000 м = 6417069,918 м ~ 6 417 км — это ответ