Energy of a free-falling, pivoting thin rod

[Oijl]

Homework Statement

The thin uniform rod in Figure 10-59 has length 4.0 m and can pivot about a horizontal, frictionless pin through one end. It is released from rest at angle θ = 40° above the horizontal. Use the principle of conservation of energy to determine the angular speed of the rod as it passes through the horizontal position.

Homework Equations

The Attempt at a Solution

I don't really know.

 

[Pythagorean]

There will be two kinds of kinetic energy you'll have to find and add together: rotational and translational. Recall your basic equations of linear and rotational motion.

 

[Oijl]

I'm sorry, but the the problem is that the fact that it's pivoting causes me hesitation with the linear equations of motion. Could you (or someone) be more specific as to how I should apply these equations?