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## Homework Statement

Richard, mass 80 kg, and Judy, who is less massive, are enjoying Lake George at dusk in a 30 kg canoe. When the canoe is at rest in the placid water, they change seats, which are 3.0 m apart and symmetrically located with respect to the canoe's center. Richard notices that the canoe moved 35 cm relative to a submerged log and calculates Judy's mass. What is it?

## Homework Equations

Center of mass equation: ([tex]\Sigma[/tex]m*x)/M

M = total mass

## The Attempt at a Solution

Ok so since they shifter positions, their center of mass did not change at all. So I set the coordinate system at the center of the canoe.

So after the canoe shifted and after they change their positions, i set both the center of masses together.

m(richard)*-1.5 + m(judy)*1.5 + m(canoe)*0 = m(richard)*1 + m(judy)*-2 + m(canoe)*.5

solving for m(judy) i got 60 kg.

Can anyone tell me what I did wrong?