A satellite is moving in a circular orbit 400km above the Earth’s surface with a measured orbital speed of 7.67kms−1. Take the mean radius of the Earth to be 6.40×103km.
(i) Calculate the distance of the satellite from the centre of the Earth.
(ii) Using the given data, determine the mass of the Earth.
(iii) From your answer in part (ii), find the average density of the Earth and comment on how it compares with the density of common surface rocks (≈3gcm−3).