Classical Mechanics (Kibble & Berkshire) · Problem 6.21
Orbits in a central field — T.W.B. Kibble, F.H. Berkshire
Physics — Mechanics · circular-motion-energy
Problem
A heavy ball is suspended from a fixed point by a light inextensible string of length b. The ball is at rest in the equilibrium position when it is projected horizontally with speed (7gb/2)1/2. Find the angle that the string makes with the upward vertical when the ball begins to leave its circular path. Show that, in the subsequent projectile motion, the ball returns to its starting point.