Introduction to the Language of Kinematics


A typical physics course concerns itself with a variety of broad topics. One such topic is mechanics - the study of the motion of objects. The
first six units of The Physics Classroom tutorial will involve an
investigation into the physics of motion. As we focus on the language,
principles, and laws that describe and explain the motion of objects,
your efforts should center on internalizing the meaning of the
information. Avoid memorizing the information; and avoid abstracting the
information from the physical world that it describes and explains.
Rather, contemplate the information, thinking about its meaning and its
applications.

Kinematics is the
science of describing the motion of objects using words, diagrams,
numbers, graphs, and equations. Kinematics is a branch of mechanics. The
goal of any study of kinematics is to develop sophisticated mental
models that serve to describe (and ultimately, explain) the motion of
real-world objects.

In this lesson, we will investigate the words used to describe the motion of objects. That is, we will focus on the language
of kinematics. The hope is to gain a comfortable foundation with the
language that is used throughout the study of mechanics. We will study
such terms as scalars, vectors, distance, displacement, speed, velocity
and acceleration.
These words are used with regularity to describe the motion of objects.
Your goal should be to become very familiar with their meaning.

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Scalars and Vectors


Physics is a mathematical science. The underlying concepts and
principles have a mathematical basis. Throughout the course of our study
of physics, we will encounter a variety of concepts that have a
mathematical basis associated with them. While our emphasis will often
be upon the conceptual nature of physics, we will give considerable and
persistent attention to its mathematical aspect.


The motion of objects can be described by words. Even a person
without a background in physics has a collection of words that can be
used to describe moving objects. Words and phrases such as going fast, stopped, slowing down, speeding up, and turning
provide a sufficient vocabulary for describing the motion of objects.
In physics, we use these words and many more. We will be expanding upon
this vocabulary list with words such as distance, displacement, speed, velocity, and acceleration.
As we will soon see, these words are associated with mathematical
quantities that have strict definitions. The mathematical quantities
that are used to describe the motion of objects can be divided into two
categories. The quantity is either a vector or a scalar. These two
categories can be distinguished from one another by their distinct
definitions:

• Scalars are quantities that are fully described by a magnitude (or numerical value) alone.
  
• Vectors are quantities that are fully described by both a magnitude and a direction.
  

The remainder of this lesson will focus on several examples of vector
and scalar quantities (distance, displacement, speed, velocity, and
acceleration). As you proceed through the lesson, give careful attention
to the vector and scalar nature of each quantity. As we proceed through
other units at The Physics Classroom Tutorial and become introduced to
new mathematical quantities, the discussion will often begin by
identifying the new quantity as being either a vector or a scalar.
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