A massive ring (radius = a and mass = M) lies on the xy plane. Calculate the force F on a test mass m at position z on the z axis.
Now assume a = 1 and GMm/a2 = 1 in some system of units.
A) What is the force on m at z = 0?
B) What is the force on m at z = a?
C) What is the maximum force on m?