Pendulum and Oscillating Motion

[cstout]

Homework Statement

A pendulum is 0.8 m long and the bob has a mass of 1.0 kg. At the bottom of its swing, the bob's speed is 1.8 m/s. What is the tension in the string at the bottom of the swing?

I don't even know how to get started on this problem, I think it has something to do with using the sin or cos but I can't find an example problem like this in my book.

 

[Tedjn]

At the bottom of its swing, the only two factors putting forces on the bob must be the rope (tension) and gravity (weight). Thus, the two together must be the net force. What else is special about the motion of a pendulum bob? How is the velocity changing?