Newton’s First Law of Motion: The Law of Inertia Physics Oct 12/15 Chapter 4 Kena Allison

What is Newton’s 1 st Law Topic Newton’s 1 st Law Facts Also called the Law of inertia Every object continues in a state of rest, or motion in a straight line at constant speed, unless it is compelled to change that state by nonzero forces exerted upon it.

So What? Topic Put Newton’s 1 st Law into your own words Facts Objects in motion stays in motion in a straight line and with the same speed AND objects at rest stay at rest unless an outside force acts upon it.

Why is it called the Law of Inertia? Topic inertia Facts Property of a body/object to resist change Think of it as an object’s laziness –If an object is at rest, then it is too “lazy” to move –If an object is in motion, then it is too “lazy” to stop Mass is how we measure inertia (kg)

Do you get the joke?

Get It?!

A video on the 1 st Law Newton's First Law Explained

Let’s take a closer look at mass Topic mass Facts The amount of matter/inertia an object has If an object has more mass, then it has more inertia (more laziness) Symbol is m The units are kilograms (kg)

Now Apply These Concepts Task Explain how a table cloth can be removed from under a plate without the plate moving Explanation The plate does not move because it has inertia and according to Newton’s 1 st Law since the plate is at rest, it wants to stay at rest. The outside force is only applied to the cloth, not the plate.

What might cause an object to change its state? Topic Force Facts Any push or pull Vector quantity Symbol is F Units are Newtons (N)

Different Types of Forces Forces Friction Force Ff Net Force FNet Normal/ Support Force FN weight w

Reach for the Stars What are the units for friction force? Newtons (N) All forces have Newtons (N) as their units

What might cause an object to change its state? Topic Friction Force Facts Force that acts between materials that touch as they move past each other that SLOWS or STOPS MOTION. Caused by irregularities in surfaces of objects that are touching

What might cause an object to change its state? Topic Net Force Facts The combinations of forces being applied Show with vectors

Equilibrium Rule When the net force is zero, an object is in equilibrium No motion (static equilibrium) Motion in straight line with constant speed (dynamic equilibrium)

Let’s Take a Closer Look at a specific type of Force Topic Normal force Facts Also called support force Upward Force Opposite force of gravity

Let’s Take a Closer Look at a specific type of Force Topic weight Facts The force of gravity on an object WEIGHT IS NOT MASS!!! Weight equals mass times gravity w = mg

Newton’s 1 st Law Relates to Real- World Safety Seatbelts and Headrest

Closing Task According to the law of inertia, why is it important to have seatbelts in cars? Why headrest? Explanation