Some fundamental basics in physics

What is Physics?

Physics is the scientific study of matter and energy and how they interact with each other.
This energy can take the form of motion, light, electricity, radiation, gravity . . . just about anything, honestly. Physics deals with matter on scales ranging from sub-atomic particles (i.e. the particles that make up the atom and the particles that make up those particles) to stars and even entire galaxies.

What are Scalars and Vectors?

Scalars are quantities which are fully described by a magnitude alone. eg 5m, 6cm etc.

Vectors are quantities which are fully described by both a magnitude and a direction. eg 5cm to north or 6 cm to south etc.

Distance and Displacement

Distance and displacement are two quantities which may seem to mean the same thing, yet they have distinctly different meanings and definitions.

Distance is a scalar quantity which refers to "how much ground an object has covered" during its motion.

Displacement is a vector quantity which refers to "how far out of place an object is"; it is the object's change in position.

Speed and Velocity

Just as distance and displacement have distinctly different meanings (despite their similarities), so do speed and velocity.

Speed is a scalar quantity which refers to "how fast an object is moving." A fast-moving object has a high speed while a slow-moving object has a low speed. An object with no movement at all has a zero speed.

Velocity is a vector quantity which refers to "the rate at which an object changes its position." Imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. While this might result in a frenzy of activity, it would also result in a zero velocity. Because the person always returns to the original position, the motion would never result in a change in position. Since velocity is defined as the rate at which the position changes, this motion results in zero velocity. If a person in motion wishes to maximize his/her velocity, then that person must make every effort to maximize the amount that he/she is displaced from his/her original position. Every step must go into moving that person further from where he/she started. For certain, the person should never change directions and begin to return to where he/she started.

Acceleration

The definition of acceleration is: Acceleration is a vector quantity which is defined as "the rate at which an object changes its velocity." An object is accelerating if it is changing its velocity.