Lecture 4: Newton’s Second Law

This set covers vocabulary related to Newton's Second Law, including definitions of various force types, fundamental forces, and the distinction between mass and weight.

Force

A push or pull that causes an object to change its motion, represented by the symbol $F$ and measured in Newtons ($N$).

Newton

The unit of force equal to a kilogram times a meter divided by a second-squared ($1,N = 1,kg \times \frac{m}{s^2}$).

Gravity

A prevalent downward force that pulls objects toward the center of the Earth due to the Earth's large mass.

Support Force

Also known as the normal force, it occurs when an object is in contact with a surface and always acts perpendicular to that surface.

Static Friction

The force required to get an object at rest to start moving.

Kinetic Friction

The force that occurs between an object and a surface as the object slides along that surface.

Air Resistance

A force that occurs when an object travels through a fluid like air; it acts in the opposite direction of motion and is proportional to the speed and form factor of the object.

Terminal Speed

The constant speed reached by a falling object when the force of air resistance becomes equal to the force of gravity.

Tension

The pulling force present in a string, cable, or other object as it holds something up, directed along the length of the string.

Elasticity

The ability of objects to deform when a force is applied and return to their original configuration once that force is removed.

Electromagnetism

A fundamental force describing the interactions of charged objects and magnetic materials.

Strong Force

The strongest of the four fundamental forces, it acts under very small scales to keep the nucleus of an atom together.

Weak Force

A fundamental force responsible for radioactive decay, fusion, and fission processes by changing one type of quark into another.

Fundamental Forces

The four categories into which all forces can be placed: gravity, electromagnetism, the strong force, and the weak force.

Newton’s Second Law

A law of motion stating that the net force on an object is equal to its mass times its acceleration ($F_{net} = m \times a$).

Net Force

The vector sum of all the individual forces that act on an object.

Mass

A measure of the "stuff" (atoms and molecules) in an object that gives it inertia and does not change based on position or location.

Inertia

An object's resistance to changes in its motion, which exists everywhere and is dependent on mass.

Weight

A force derived from gravity that is equal to an object's mass times the acceleration due to gravity ($W = m \times g$).

$$g$$

The acceleration due to gravity, which is approximately $-9.8\,m/s^2$ on Earth.