If the carts are getting different momentums, as they appear to be, then they must be experiencing different impulses. That's in contrast to your idealized diagram where the impulses would be the same.
Could you look into problem solution, please.
http://knol.google.com/k/alex-belov/the-wheels/1xmqm1l0s4ys/18#"Let's assume the law of momentum conservation always works in simplest form. In this case, the forces on both sides of spring are equal by value and induce translational motions for solid block and rolling objects on both platforms. However, which force induce rotational motion for rolling objects on one platform? The solid block doesn't conduct rotational motion on other platform. On one platform, the rolling objects rotate on opposite direction for each other and have same angular momentum by value and opposite direction. However, need a force to induce this rotation. The asymmetrical force cannot exist during interaction. Therefore, the assumption where law of momentum conservation exist in simple form during complex interaction is wrong."
Can you explain how the spring works. It doesn't look anything like the diagram. The high speed parts are a concern because they'll carry a lot of momentum that's assumed to be zero in the diagram.
Actually same. The one cart repulses form another through spring. It does not what spring shape is. The spring must have same forces on both sides on ideal model.
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BTW.
This is the force resistance test.
http://www.youtube.com/watch?v=AsQ9GsRThwQ&feature=player_embeddedIf you see there both carts mostly have same distance.
