AP Physics C: Mechanics Flashcards: Kinetic and Static Friction
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 10 cards to help you master important concepts.
What is the formula for the magnitude of the kinetic friction force?
The magnitude of the kinetic friction force is the product of the coefficient of kinetic friction and the normal force, given by the equation $|\vec{F}_{f,k}|=\mu_{k}F_{N}$.
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What is the formula for the magnitude of the kinetic friction force?
The magnitude of the kinetic friction force is the product of the coefficient of kinetic friction and the normal force, given by the equation $|\vec{F}_{f,k}|=\mu_{k}F_{N}$.
A car is parked on a hill and remains stationary. What is the primary role of friction in this situation?
Static friction adopts the necessary value and direction to prevent the car from slipping or sliding down the hill.
What does the inequality $|\vec{F}_{f,s}|\le\mu_{s}F_{N}$ imply about static friction?
This inequality implies that static friction is a variable force that adjusts its magnitude to prevent motion, but it has a maximum possible value it cannot exceed.
How is the magnitude of the static friction force determined?
Static friction's magnitude is not fixed; it adopts the value required to prevent motion, up to a maximum value defined by the inequality $|\vec{F}_{f,s}|\le\mu_{s}F_{N}$.
What two factors determine the magnitude of the kinetic friction force?
The magnitude of the kinetic friction force is determined by the coefficient of kinetic friction ($\mu_{k}$) and the normal force ($F_{N}$) the surface exerts on the object.
If a box is sliding across a floor, which type of friction is acting on it?
Kinetic friction is acting on the box because it is in motion relative to the surface of the floor.
What is the role of the coefficient of kinetic friction ($\mu_{k}$)?
The coefficient of kinetic friction is the constant of proportionality in the equation $|\vec{F}_{f,k}|=\mu_{k}F_{N}$, relating the kinetic friction force to the normal force.
What is kinetic friction?
Kinetic friction is the friction that exists between two surfaces when they are moving relative to each other.
You push a heavy desk, but it doesn't move. What force opposes your push?
Static friction opposes your push, adopting a value and direction required to prevent the desk from slipping or sliding.
What is static friction?
Static friction is the friction that prevents an object from slipping or sliding on a surface when a force is applied.