Usually, we do not walk or even stand on a lightweight boat or raft because of the danger of falling into the water. If you have ever stepped off a small boat onto a dock, however, you have probably noticed that the boat moves away from the dock as you step toward the dock or out of the boat. A heavy dog running on a long lightweight raft presents a similar situation. At first, the raft and the dog are at rest with respect to the water (see figure A below) so that
Usually, we do not walk or even stand on a lightweight boat or raft because of the danger of falling into the water. If you have ever stepped off a small boat onto a dock, however, you have probably noticed that the boat moves away from the dock as you step toward the dock or out of the boat. A heavy dog running on a long lightweight raft presents a similar situation. At first, the raft and the dog are at rest with respect to the water (see figure A below) so that
The dog then runs on top of the raft at
with respect to the water (see figure B below). The dog has one sixth the mass of the raft. Find an expression for the velocity of the raft after the dog began running. (Use the following as necessary: vd.)

This is a question regarding the moving of the center of mass.
For a two-body system, the velocity of the center of mass is given by the formula:
where
is the change in velocity of the center of mass.
is the mass of body 1
is the change in velocity of body 1
is the mass of body 2
is the change in velocity of body 2
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