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clope023

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**[SOLVED] Falling rod with a mass on either end**

## Homework Statement

A wooden rod of negligible mass and length 85.0cm is pivoted about a horizontal axis through its center. A white rat with mass 0.520kg clings to one end of the stick, and a mouse with mass 0.250kg clings to the other end. The system is released from rest with the rod horizontal.

If the animals can manage to hold on, what are their speeds as the rod swings through a vertical position?

## Homework Equations

(K1a + K1b) + (U1a + U1b) = (K2a + K2b) + (U2a + U2b)

U = mgR, R = 1/2d of the rod

K1 = 0

U2 = 0

## The Attempt at a Solution

(magR + mbgR) = 1/2v^2(ma + mb)

gR (ma+mb) = 1/2v^2 (ma+mb)

2gr = v^2, v = [tex]\sqrt{2gr}[/tex]

v = 2.9m/s wrong

not sure what I'm doing wrong here.

any help is appreciated.

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