Question

When you sit on a chair, what is the reaction force to you weight(the downward action force)?

Answer 1

When you sit on a chair, your body exerts a downward force on the chair due to your weight (this is the action force). According to Newton's third law of motion, for every action, there is an equal and opposite reaction. Therefore, the reaction force to your weight is the upward force that the chair exerts on you. This upward force is equal in magnitude and opposite in direction to the downward force that you exert on the chair. Hence, while you apply a downward force due to your weight, the chair exerts an upward normal force that supports you.