Transcript lesson 1 Newton_s First Law of Motion

Inertia
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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.
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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.
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Using the first law of motion, describe
whiplash.
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Place a piece paper below a filled water
bottle.
Your task is to remove the piece of paper
without touching the water bottle.
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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.
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Watch the following video and describe what
is happening based on the first law of
motion.
http://www.youtube.com/watch?v=cuG8sIiV8
iQ
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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.
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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)
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Galileo knew Newton’s First Law well before
Newton…
However, Galileo was concerned with how
things moved, not why they moved.
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Let’s look at the following picture and
situation… (pg. 45 of textbook)
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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=aCqQzrPC
cFM
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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.
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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
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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
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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.