Newton came up with three laws of motion. Each lesson in this grouping will cover one of the
laws, followed by a description and a sample problem.
Newton's First Law of Motion, often called the Law of Inertia, basically says that an object
at rest will stay at rest and an object in motion will continue in a straight line unless acted
on by an outside and unbalanced force.
That will, or staying power, that an object has is called inertia. There are two different
kinds of inertia, linear and angular. This particular lesson will have to do with linear inertia,
although we will get into angular inertia later.
It is really very simple to find out how much linear inertia an object has. The conversion
equation is below.
m = linear inertia
No, that's not a misprint, that's it. If an object has a mass of 50kg, it has 50kg of
inertia. Let's do a sample problem.
If an object comes off a hill at 20m/s and travels along a frictionless surface, what will
it's velocity be after 100,000 meters?
Hmmm... At the beginning of the problem the object is traveling at 20m/s. It travels
100,000m without obstruction, so at the end of its journey it would be traveling... 20m/s.
Now sure, that was a bit juvenile, but its purpose was to demonstrate that no matter how far
or for how long an object travels, it will always travel in a straight line and go forever unless
acted upon by an unbalanced force.
Newton's Second Law is one of the most powerful in introductory physics.
