Satellites

[le93]

Bit stuck on question C. Answers to A and B are; C and B respectively. Could someone explain question C to me....

Two satellites S1 and S2 are in circular orbits around the Earth.
Their respective orbital radii are R and 2R. The mass of S1 is twice
that of S2. Calculate the value of the following ratios and use the
following answer key: A 1, B √2, C 1/√8, D 4.
a orbital period of S1/orbital period of S2
b orbital speed of S1/orbital speed of S2
c acceleration of S1/acceleration of S2.

Thanks

[xZero]

a = G*M/R^2, let the acceleration of S1 be a1 = G*M/R1^2, let the acceleration of S2 be a2 = G*M/R2^2

a1/a2 = G*M/R1^2 / G*M/R2^2 = R2^2 / R1^2, since R2 = 2R1, a1/a2 = (2R1)^2/R1^2, a1/a2 = 4

[le93]

thanks