# Two people in spaceshift shift seats

#### diffusion

Two people in a spaceship shift seats....

1. Homework Statement
Simma (mass 60kg) and Stan (mass 90kg) are testing an ultralight spacepod. They swap seats, with the seats being 4.0m apart, located at equal distances from the center of mass of the space-pod. The space-pod's mass is 50kg. Why does the space-pod not move after they take their new seats? How far does it move and which way? All observations are in the frame in which the space-pod was initially stationary.

2. Homework Equations
p$$_{1}$$ + p$$_{2}$$ + p$$_{3}$$ = $$\Sigma$$P
center of mass = m$$_{2}$$ / m$$_{1}$$ + m$$_{2}$$ x d

3. The Attempt at a Solution
There are two questions here: How far does the spacepod move when Simma and Stan change seats, and why does it stop after the take their new seats.

Unless I'm over looking something, the answer to the second question is simply that the net momemtum = 0, so the spacepod is at rest.

In order to find out how far it moves, I figured I could try to figure out the change in position of the center of mass, and that is how far the spacepod moves? Not really sure how to approach it.

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#### diffusion

Re: Two people in spaceshift shift seats....

Anyone? Just need a little steering in the right direction, the rest I should be able to do by myself.

#### Redbelly98

Staff Emeritus
Science Advisor
Homework Helper
Re: Two people in a spaceship shift seats....

In order to find out how far it moves, I figured I could try to figure out the change in position of the center of mass, and that is how far the spacepod moves? Not really sure how to approach it.
Yes, that is exactly how to approach it Since the center-of-mass of pod+Simma+Stan does not move,

Δcom of pod = -Δcom of (Simma & Stan)

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