Physics
Treating Normal Force as Always Equal to Weight
Students set the normal force equal to weight in every situation.
Quick check
Why students make it
On a flat floor with no vertical acceleration, , so that case feels like a rule. The normal force is a contact force that adjusts to the situation, not a copy of the object's weight.
The rule done right
The normal force is the force from a surface perpendicular to the surface. Find it from Newton's second law in the perpendicular direction, so equals only when the perpendicular forces and acceleration make that true.
Related resources
-
Physics, Normal Force and Apparent Weight Infographic -
Free Body Diagrams (Complete Guide) Infographic -
Physics, Vector Components and Resolution Infographic -
Physics, Forces on an Inclined Plane Infographic -
Newton's Second Law Infographic - Newton's Laws & Forces Cheat Sheet
- Free Body Diagrams Reference Cheat Sheet
- Friction, Normal Force & Inclined Planes Cheat Sheet
- Friction Coefficients Reference Cheat Sheet
- Friction Worked Examples Cheat Sheet
- Science, Newtons Laws of Motion Worksheet
- Physics, Newton's Laws, Free Body Diagrams and Net Force Worksheet
- Science, Free Body Diagrams Worksheet
- Forces & Motion Worksheet
- Physics, Newton's Third Law Worksheet
- Forces & Free-Body Diagram Tool Tool
- Vector Addition & Components Explorer Tool
- Kinematics Solver Tool
- Balanced Forces Lab Lab
- Friction & Inclined Plane Lab Lab
- Buoyancy Lab Lab
- Newton's First Law Lab Lab