Chapter 2.1: Aristotle on Motion

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Chapter 2.1 Aristotle on Motion

• Force causes motion
• Natural motion and violent motion
• Natural motionnot caused by forces
• Smoke and bouldersup, down
• Planets and the heavenscircular
• Violent motionpush or pull
• Proper state of objects is at rest
• Thought the earth did not move

4th century BC
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Chapter 2.2 Copernicus and the Moving Earth (not
in book)

• Changed the view of the world
• Earth and other planets revolve around the sun
• Avoided persecution by hiding his discoveries
• Close to death he released his ideas for print
• De Revolutionibus

1473-1543
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Chapter 2.2 Galileo on Motion

• Championed Copernicus ideas, was persecuted and
  put on trial
  
• Proved through experimentation force is not
  needed to keep an object moving
  
• Explained friction
• Every object resists change to its state of
  motionInertia!

1564-1642
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Do Now!!!

• If you drop a bowling ball and a feather from the
  top of the Empire State Building which will hit
  the ground first? Explain.
  
• What about if the Empire State building was in a
  vacuum? Explain

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Chapter 2.2 Galileo on Motion

• Galileo showed that experiment, rather than
  logic, is the best test of knowledge
  

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Chapter 2.3 Speed

• Speed (Change in Position)
  (Change in time)
  
• S (? d) / (? t)
• Are speed and velocity the same?
• NO

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Speed Vs. Velocity

• Speed is a scalar quantity.
• Speed just has magnitude
• 55mph
• 10degrees Celsius
• Velocity is a vector quantity.
• Velocity has both magnitude and direction
• 55mph due north
• 10N at 45degrees
• v (? d) / (? t)

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Chapter 2.4 Motion is RELATIVE???
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Do now!

• A plane flight from NYC to LA is 5.50 hours. The
  distance from NYC is 3000.0 miles. How fast is
  the plane flying? Use the GUESS method!
  
• Motion is relative! Explain (in detail) what
  this statement means. Give an example of this
  statement.
  

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Chapter 2.5 Newtons Law of Inertia (Newtons
1st Law of)

• Newtons First LawEvery object continues in a
  state of rest, or of motion in a straight line at
  a constant speed, unless it is compelled to
  change that state by forces exerted upon it.
• Objects in motion tend to stay in motion
• objects at rest tend to stay at rest.

1643-1727
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Do Now!!!!!!

• The space shuttle (in orbit) traveled 18000.0 km
  at a speed of 17,580mph (7860m/s). How long did
  it take to cover this distance?

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Chapter 2.6 Net Force

• Net forceThe combination of all forces acting on
  an object
  

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Chapter 2.7 Net Force

• Support Force NORMAL FORCE if object is in
  equilibrium the support force is equal and
  opposite the force of gravity

2N
2N
4N
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2.7 Net force
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Net force
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Current 400 N
Wind 200 N
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Bull blast 1050 N
Horizontal Force 325 N
Fg 535 N
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End Chapter 2
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Chapter 4.7 Equilibrium
See Figure 3.9 in the text.

• Support forcenormal force at right angles to
• Equilibrium is when net force is equal to
  zerothe object is in a state of rest
  

Compression
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Chapter 4.7 Equilibrium

• How about tension?
• Tension is shared equally among vertical
  supports
  

2 N
2 N
4 N
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Chapter 4.8 Vector Addition of Forces

• Equilibrium is when net force is equal to
  zerothe object is in a state of rest
  
• Tension increases as the angle of the supports
  increases
  

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Chapter 4.9 The Moving Earth Again
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Chapter 3.3 MassA Measure of Inertia

• Mass is the amount of material in an object, or a
  measure of its inertia
  
• Mass is not volume
• Volumea measure of space, cubic cm, cubic m, and
  liters
  
• Mass is measured in kilograms

Which is more difficult to set into motion?
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Chapter 4.5 MassA Measure of Inertia

• Mass is not weight
• Weight is a measure of the gravitational force
  acting on an object
  
• Depends on location
• Mass and weight are proportional

Weight on Mars 40 of that on Earth.
Jump 2.5 times higher!
Talk about hang time!
On Mars
On Earth
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Chapter 4.5 MassA Measure of Inertia

• One Kilogram weighs 9.8 Newtons
• The unit of force is the NewtonN
• Learn how to convert kg to N and vice versa
• Weight mass x acceleration due to gravity or
  weight mg