When you sit in a chair, what force does the chair exert on you to support your weight?

When you sit in a chair, what force does the chair exert on you to support your weight?

• A. Normal force
• B. Friction
• C. Gravitational force
• D. Applied force

Answer: (A)

The main idea is the normal force, the contact force that a surface exerts on an object perpendicular to that surface. When you sit, gravity pulls you downward. The chair pushes upward on you, perpendicular to the seat—this is the normal force. If you’re sitting still, the normal force balances your weight, so its magnitude equals mg. This upward push is what supports your weight. Friction acts along the surface and doesn’t provide the vertical support in this situation. The gravitational force is the downward pull from the Earth on you, not the chair’s push. An applied force would be a force you actively exert, not the force the chair applies to you.

The main idea is the normal force, the contact force that a surface exerts on an object perpendicular to that surface. When you sit, gravity pulls you downward. The chair pushes upward on you, perpendicular to the seat—this is the normal force. If you’re sitting still, the normal force balances your weight, so its magnitude equals mg. This upward push is what supports your weight.

Friction acts along the surface and doesn’t provide the vertical support in this situation. The gravitational force is the downward pull from the Earth on you, not the chair’s push. An applied force would be a force you actively exert, not the force the chair applies to you.