✔ 最佳答案
You have used the wrong figure for r.
r is the distance of the stationary satellite from the centre of the earth. It can be found from the following centripetal force equation.
GmM/r^2 = mrw^2
where G is the Universal Gravitational Constant
M and m are the masses of the earth and satellite respectively
w is the angular speed of the satellite
Hence, r^3 = GM/w^2
Put in the values of G = 6.67 x 10^-11 m^3/kg.s^2, M = 5.97 x 10^24 kg and w = 2.pi/T = 7.27 x 10^-5 s^-1
the value of r is calculated to be 4.22 x 10^7 m
Hence, v = (4.22x10^7) x (2.pi/T) = 3071 m/s