Oak Bay Secondary Academic Study Notes: Pages 75-130 (2012-2013)

Inertia

The tendency of an object to resist any change in its state of motion (to keep doing whatever it is already doing). Depends on mass — more mass means more inertia. Inertia is a property of matter that describes how much an object will resist changes to its velocity, including changes to the object's speed or direction.

Newton's First Law (Law of Inertia)

An object at rest stays at rest, and an object in motion stays in motion at a constant velocity unless acted upon by a net external force.

Newton's Second Law

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass: F = ma.

Newton's Third Law (Law of Action and Reaction)

For every action force one body exerts on a second body, the second body exerts an equal and opposite reaction force on the first, over the same time interval.

Inertial mass

A measure of an object's resistance to acceleration when a force is applied; determined using F = ma.

Gravitational mass

The mass of an object as measured by comparing the gravitational force on it to a standard mass (e.g., on a balance scale). Numerically equal to inertial mass

Unbalanced (net) force

The overall force remaining after all forces acting on an object are combined; it is what causes acceleration (F = ma).

Free-body diagram

A diagram that isolates one object and shows every force acting on it (gravity, normal force, applied force, friction, etc.) as arrows.

Ideal conditions

A simplifying assumption (usually zero friction/air resistance) used in physics problems so that only the motion being studied is considered.

Coefficient of kinetic friction (μ)

A unitless ratio describing how much friction force exists between two surfaces relative to the normal force: μ = F_f / F_N

Normal force (F_N)

The support force exerted by a surface perpendicular to that surface, balancing the perpendicular component of other forces (like gravity) on a resting object

F = ma

Newton's Second Law equation. F = net force (N), m = mass (kg), a = acceleration (m/s²). 1 N = 1 kg·m/s².

F_f = μF_N

Equation for kinetic friction force. F_f = friction force (N), μ = coefficient of friction (no units), F_N = normal force (N).

Newton (N)

SI unit of force; the force needed to accelerate a 1 kg mass at 1 m/s². Equivalent to 1 kg·m/s².

Action force