Newton’s 1st Law of Motion8th Grade Science

Newton’s 1st Law of Motion

This law is AKA "the law of inertia".

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.

Newton’s 1st Law of Motion

What Does it 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.

These pumpkins will not move unless acted on by an unbalanced force.

Example

Once airborne, unless acted on by an unbalanced force (gravity and air – fluid friction), it would never stop!

Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever.

WAIT! Then why do objects in motion slow down and then stop without an outside force?

Critical Writing (Think, Pair, Share)

Remember the forces we talked about last week?

Write down possible forces acting on the object that we can’t see.

Friction in Action

Slide a book across a table and watch it slide to a rest position. The book comes to a rest because of the presence of a force - that force being the force of friction - which brings the book to a rest position.

Why Does it Stop?

In the absence of a force of friction, the book would continue in motion with the same speed and direction - forever! (Or at least to the end of the table top.)

1st Law in Action

You have 1 minute to discuss the questions with your shoulder partner:

1. What is the motion in this picture?

2. What is the unbalanced force in this picture?

3. What happened to the skater in this picture?

Newton’s 1st Law in Action

Don’t let this be you. Wear seat belts!

Because of inertia, objects (including you) resist changes in their motion. When the car going 80 km/hour is stopped by the brick wall, your body keeps moving at 80 km/hour.

Penny and Cup DemonstrationProduct: How does this demo relate to Newton’s 1st Law of motion? (complete sentences)