Answer to Question #82155 in Mechanics | Relativity for Thomas

Question

A bullet of mass m and speed v is fired at an at rest pendulum bob. The bullet goes through the bob, and exits with a speed of v/3. The pendulum bob is attached to a rigid pole of length L and negligible mass. What is the minimum value of v such that the pendulum bob will barely swing through a complete vertical circle?
I have no idea how to start this, have never been good at problem solving really.