inertia. every object continues in a state of rest, or of motion in a straight line at constant...

Inertia

Every object continues in a state of rest, or of motion in a straight line at constant speed, unless it is compelled to change that state by forces exerted upon it.

Or… An object in motion tends to stay in motion, and an object at rest tends to stay at rest.

Using the first law of motion, describe why a person will hit their head on the windshield if they are not restrained with a seatbelt during a head-on collision.

Using the first law of motion, describe whiplash.

Place a piece paper below a filled water bottle.

Your task is to remove the piece of paper without touching the water bottle.

Open the cap of the water and place an index card on top of the bottle.

Place a skittle on top of the index card. Challenge: get the skittle into the water.

Watch the following video and describe what is happening based on the first law of motion.

http://www.youtube.com/watch?v=cuG8sIiV8iQ

Observe a cart rolling along the floor. After we push it, why does it continue to

roll? What force is keeping it going?? NO FORCE keeps it going.

Imagine you are in the back of your friend’s car with 2 other buddies and you are in the center. As the car turns to the right, which buddy will you squish?

What is causing this to happen? (Describe using Newton’s 1st Law)

Galileo knew Newton’s First Law well before Newton…

However, Galileo was concerned with how things moved, not why they moved.

Let’s look at the following picture and situation… (pg. 45 of textbook)

Mass is the measure of inertia.

Mass is NOT volume Consider a fluffy pillow vs. a shot put.

Mass is not weight Consider the following demonstration… http://www.youtube.com/watch?v=aCqQzrP

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Metric units are kilograms

1 kilogram is approximately the weight of a baseball bat or a medium sized pumpkin, or a high school discus.

English units are slugs.

Weight = mass * acceleration due to gravity

Acceleration due to gravity = 9.8 m/s/s on Earth.

Units for weight… Metric units are Newtons English Units are Pounds

An object that is motionless DOES NOT MEAN that there are no forces acting on the object.

If an object is motionless or at a constant linear speed, it is said to be at EQUILIBRIUM.

There is no net force on the object

A book on a table

A person standing on the ground Normal force explained

A traffic light hanging from wires in the middle of an intersection.