# Inertia!.

## Presentation on theme: "Inertia!."— Presentation transcript:

Inertia!

History ~300 B.C.E. Aristotle (Greek)
Divided motion into two categories: Natural motion: straight up or straight down Violent motion: result of force Any movement “against nature” was because of a force Everything rests on Earth; Earth is too big to move

Copernicus ~1500 C.E. Studied astronomy
Observed that astronomy worked better if Sun was center of solar system Theorized that the Earth did move

Galileo ~1600 C.E. Argued that objects only stop moving because of friction Friction: force that opposes movement Occurs between two touching objects :., objects in motion should stay in motion without friction

Inertia Galileo called this idea inertia
Inertia allows objects to resist changes in motion

Newton ~1700 C.E. Re-stated Galileo’s ideas in his 1st law of motion
Objects continue at rest or in a straight line at a uniform speed, unless acted on by a nonzero net force Newton’s First Law of motion (aka law of inertia)

Vocabulary Friction Inertia Law of inertia Mass Weight newton

Objects at rest An object at rest will stay there unless an outside force acts upon it That force upsets the equilibrium and will start the object moving

Objects in motion Once in motion, the net force becomes zero again
Only another force will make it slow down or change direction

What does the amount of inertia depend on?
Mass

Mass is not….. Volume (a large size does not equal a large mass)
Weight (weight depends on gravity, which is different in different places)

Mass is Inertia Mass is the amount of matter in an object
The more mass, the more inertia an object has Mass is measured in kilograms (kg) Weight is the force of gravity Weight is measured in newtons (N)

Relative Motion Does a rock move sideways as it falls?
Why doesn’t it, if the Earth is moving?

Relative Motion Objects move with the earth
The rock is moving with the earth as it falls, so it does not seem to move sideways

Relative Motion

Relative Motion High speed vehicles demonstrate this concept.
Dropping a rock in a plane has the same effect. The rock moves with the plane