Angular speed uniform rod problem

[tigerlili]

Homework Statement

The thin uniform rod in Fig. 10-52 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. Assume free-fall acceleration to be equal to 9.83 m/s2.

Homework Equations

i really have no idea where to start this :/

The Attempt at a Solution

 

[rock.freak667]

Well the question says to use the law of conservation of energy.

Since we are talking energy and rotation, rotational kinetic energy should be in your energy equation.


At the angle of 40 degrees, when just held at that position (such that it is at rest), what type of energy does it possess? When it passes through the horizontal plane, what type of energy does it have?

 

[tigerlili]

thanks for your help, i actually got it :)