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**1. The problem statement, all variables and given/known data**

In figure (a), a 5.4 kg dog stands on a 16 kg flatboat at distance D = 6.1 m from the shore. It walks 2.1 m along the boat toward shore and then stops. Assuming no friction between the boat and the water, find how far the dog is then from the shore.

**2. Relevant equations**

Center of mass = (x1m1 + x2m2)/(m1+m2)

**3. The attempt at a solution**

Since the center of mass cant change i set the two equal.

x1 (position of dog) = 6.1

x2 (center of canoe) = x

(6.1*5.4 + 16x2)/21.4 =

(5.4*(6.1-2.1) + 16(x2+Δcom))/21.4

which gives the change in the center of mass of the boat is .70875 so the dog only moves 2.1-.70875 and starting 6.1 meters away he is 4.70875 but thats wrong