So I am a person sitting on a chair that has wheels. Now, the question is - can I push the chair when I am sitting on the chair and have nothing to push against? [other than the chair] Whenever i try to push against the chair, friction with the ground seems to pull it back. According to Newton's 3rd Law, each force produces an equal and opposite force. So as I push against the chair, the equal and opposite force acts on the me + chair system to move it back. But part of the force is friction against the me + chair system, and part of it is the chair against me. So I refrain from moving and the net effect is that the chair and I go in the direction of where i push, but with some recoil. This logic probably applies to cars as well [since the engines have nothing to push against, other than the car itself] Note that I have no contact whatsoever with the floor.