BEFORE WE BEGIN...
This section will deal with the concept of FORCE.
You already understand acceleration, which
is an integral part of any force.
However, we have not yet gone into the other part of
force, which is MASS.
"Mass" can be a confusing term.
It has been defined before as "how much matter is in
an object."
Many people think of mass as the number they see on their
bathroom scale.
Physicists define it as a measure of inertia.
What's inertia?
We have all seen the commercials with the crash test
dummies hitting a dashboard. They keep right on moving toward the
dashboard when the car crashes because they have inertia (and
therefore also have mass).
So inertia is a tendency to maintain present motion (moving
or not).
Mass is anything that has inertia.
Example: A ball sits motionless on a floor. If the
ball is to move, something must happen to it. It will remain sitting
still until some action moves it. The ball has inertia.
A ball rolls across a floor. It will not stop until
something happens. It hits a barrier. Friction with the floor
slows then stops it. The ball will roll unless
something affects it.
NOTE: 2000 years ago, Aristotle
noticed that all sliding or rolling objects will come to a stop, so he
taught his students that the natural state of things was to stop.
He didn't know about friction.
Galileo realized that without
friction, a ball would continue on forever.
Newton seems to get the
credit for this due to his statement we refer to as "Newton's First Law".
NEWTON'S FIRST LAW OF MOTION:
An object at rest remains at rest, and an object in motion maintains that
motion until it experiences some net force.