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?
Best Answer
In free space, this would be impossible, but there's friction, so if you impulse the chair forward, by moving yourself a little back (by conservation of momentum the chair must move forward), and then you get back to you initial position, the chair will move back again, but there's friction and energy is being lost during the process so the distances will be smaller and the chair, at the end, will be a little bit moved forward.