When you sit still in a chair with your feet on the ground and your back pressing against the back of the chair, are the forces acting on you balanced? Explain.
Are the forces acting on you balanced if you lift your feet off the floor but remain still? Explain.
Lastly, if you tilt back in your chair (not recommended!) and you fall backwards to the floor, are the forces acting on you balanced while you are falling? Explain.
How about after you have hit the floor? Explain.