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## Homework Statement

This problem is from the 2015 AP Physics C Mechanics free response, question 3 part b.

https://secure-media.collegeboard.org/digitalServices/pdf/ap/ap15_frq_physics_c-m.pdf

## Homework Equations

K = 1/2Iω

^{2}

U = mgh

## The Attempt at a Solution

The potential energy of the bar when it's horizontal gets transferred to kinetic energy when vertical, so I originally had the equation mgL = 1/2(1/3ML

^{2})ω

^{2}

However, the scoring guidelines say that the change in height should be L/2, not L, resulting in a potential energy of mgL/2. Could someone explain why the change in height should be L/2 and not L?

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