The force between two masses separated by a distance r is given as:
Where F is the attractive force between 2 masses, m1 and m2, r is the distance between the centres of the masses and G is the universal gravitation constant, which is
The mass of the earth () is far greater than the mass of the sputnik (). Therefore . The mass of the sputnik is neglected, therefore:
But F is actually centripetal acceleration, a = v²/r