1-D Forces

Definitions and Terms

Force Diagram/Free Body Diagram

Net Force/Sum Of Forces

Equilibrium/ Fnet=0

Normal

Inertia

Newton's Discovery

Newton's First Law:

I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

Newton's Second Law:

II. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.

Newton's Third Law:

III. For every action there is an equal and opposite reaction.

FOUR FUNDAMENTAL FORCES

There are 4 fundamental forces that have been identified. In our present Universe they have rather different properties.

Properties of the Fundamental Forces

The strong interaction is very strong, but very short-ranged. It acts only over ranges of order 10^-13 centimeters and is responsible for holding the nuclei of atoms together. It is basically attractive, but can be effectively repulsive in some circumstances.
The electromagnetic force causes electric and magnetic effects such as the repulsion between like electrical charges or the interaction of bar magnets. It is long-ranged, but much weaker than the strong force. It can be attractive or repulsive, and acts only between pieces of matter carrying electrical charge.
The weak force is responsible for radioactive decay and neutrino interactions. It has a very short range and, as its name indicates, it is very weak.
The gravitational force is weak, but very long ranged. Furthermore, it is always attractive, and acts between any two pieces of matter in the Universe since mass is its source.