# How does this chair move?

I have a chair like this(shown in figure). I was kneeling on the part where we sit. I just gave a sudden push to the part where we rest the back, without moving my legs. I found that the chair is moving little in the direction I applied the force. I couldn't find any reason why this chair would move forward because I am inside this system and no external force is coming from outside. When I apply the force on it , equal amount of force I am applying there on the seat in the opposite direction, so there should not be any movement.

I tried this experiment again right now. Now holding on the handles of the chair. Did the same thing. Again found the chair moving.

Where I am wrong and how does the chair move?

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Cool, I am just sitting on an almost identical one. ;-) google.cz/… – Luboš Motl Jan 10 at 18:53
@LubošMotl: Did you try above experiment? – Inquisitive Jan 10 at 18:54
Sure, it's just momentum conservation, isn't it? Or, a better law: the conservation of the horizontal location of the center-of-mass of the whole system chair+you. So when your body moves in one direction, the chair moves in the opposite direction. However, all these things are modified by friction - which also differs depending on the weight on each wheel, and so on. – Luboš Motl Jan 10 at 19:04