Practise equating gravitational and centripetal forces to calculate orbital speed, radius, period or mass, and interpreting changes with radius or central mass.
A spherical planet can be considered as a point mass at its centre.
A satellite is in a circular orbit around the planet.
Explain, with reference to your answer in (b)(i), why the path of the satellite is circular.
field lines show force (on satellite) is towards centre of planet
or
velocity of satellite is perpendicular to field lines
B1
(gravitational) force perpendicular to velocity causes centripetal acceleration
B1