According to Newton's first law...

An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

This law is often called
"the law of inertia".

What does this mean?

This means that there is a natural tendency of objects to keep on doing what they're doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain this state of motion.

Let's study the "skater" to understand this a little better.

What is the motion in this picture?

What is the unbalanced force in this picture?

What happened to the skater in this picture?

This law is the same reason why you should always wear your seatbelt.

Now that you understand
Newton's First Law of Motion,
let's go on to his Second Law of Motion.

Home || Next