JOAN CARTAN-HANSEN, HOST: The world is full of motion and motion happens because of force.

So how do force and motion move your world?

Let's take a few carnival rides and find out.

[MUSIC] A force is pretty simply.

It's basically just a push or a pull.

So a force is a change in motion.

Gravity pulls you down, and the ground pushes you up.

When forces are in balance nothing happens, and you don't notice it.

It's when they get out of balance that things happen.

Ready?

Gravity is the force of attraction between things.

It's what makes things fall.

(SCREAMING) There are three laws of motion discovered by Sir Isaac Newton.

An object that isn't being pushed or pulled by a force either stays still or keeps Moving in a straight line at a constant speed.

(SCREAMING) STUDENT: Wait a minute, gravity pulled me down in a straight line.

Why did we stop?

CARTAN-HANSEN: Well, Newton's first law is all about inertia.

Inertia is an object's tendency to resist any change in its motion.

A body at rest stays at rest.

A body in motion stays in motion.

If gravity was the only force, you'd just keep sliding.

Another force called "friction" slows you down, and you stop.

Forces make things move.

The bigger the force or the lighter the object, the greater the motion.

Say you push a toy along the street, it's pretty easy because the toy is light, and you can push or pull with a lot of force.

The more force, the faster it moves or accelerates.

STUDENT: Good aim!

CARTAN-HANSEN: Say you try to push or pull something really big, it would take a lot of force to get it to move.

Every action has an equal and opposite reaction.

Forces act in pairs.

When the space shuttle lifts off, the burning gas pushes out the engine and lifts the shuttle.

When you hit your friend with a bumper car, the force pushes him away, but the force of his car pushes you back the same amount of force.

Hit him softly, you both move just a little.

Hit him hard, woo-hoo, equal and opposite reaction.

The laws of motion are the basis for the science of physics.

They apply to all the particles in the universe from the smallest atom to even the biggest planets.

Even this roller coaster.

STUDENT: Stay at rest until acted on by an outside force; that's Newton's first law.

And when an engine pulls the cars up the hill, that's Newton's second law.

Applying a force makes an object move.

And how does the third law apply?

CARTAN-HANSEN: And for every action, there's an equal and opposite reaction.

First, we go up, then we go down!

[SCREAMING] CARTAN-HANSEN: If you want to learn more about force and motion, check out the Science Trek website.

You'll find it at Science Trek dot org.

[MUSIC] ANNOUNCER: Presentation of Science Trek on Idaho Public Television is made possible through the generous support of the Laura Moore Cunningham Foundation, committed to fulfilling the Moore and Bettis family legacy of building the great state of Idaho.

By the Idaho National Laboratory, mentoring talent and finding solutions for energy and security challenges, by the Friends of Idaho Public Television, and by the Corporation for Public Broadcasting.