Friction Force Equation
Reference from the original Physics I textbook.
- Friction Force Equation
Static friction magnitude: . At impending slip, fₛ,max = μₛN.
Kinetic friction magnitude: . Friction acts along the contact surface; the normal force acts perpendicular to it.
fₛ, fₖ = friction magnitudes (N); N = normal-force magnitude (N); μₛ, μₖ = dimensionless friction coefficients.
- Related Glossary Terms
Friction Force, Normal Forceⓘ, Table 1.4.1: List of Coefficient of Frictions
- Index
Chapter 1 - For Future Reference - Forces as Vectors
Chapter 1 - For Future Reference - Forces as Vectors
Reviewed physics notes (3)
These corrections keep the original lesson’s purpose while fixing errors in the source edition.
- Static friction equality is only its maximum. — Reference 1
- A friction vector cannot equal a scalar multiple of the perpendicular normal-force vector. — Reference 1
- Uses magnitudes consistently. — Reference 1
Glossary and deeper reading · 2 refreshers
These editorial refreshers supplement the reading. Definitions and examples are added guidance; original source wording and recorded answers remain in their original context.
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Force
A force describes an interaction that can change an object’s momentum. It is a vector measured in newtons, so both size and direction matter when forces are added. For example, a rope can pull a cart while the floor exerts friction in another direction.
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Normal force
A normal force is a contact force perpendicular to the local surface of contact. Its magnitude is set by the motion and the other forces, so it need not equal the object’s weight. For example, a wall’s normal force on a leaning ladder points horizontally rather than upward.