Transcript Dynamics

What is dynamics?

Dynamics is the study of forces.
What are forces?

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Push or pull on an object
What are some different types of forces?
 Applied force
○ Action caused by touching
 Gravitational force
○ Caused by gravity
 Normal force
○ Support force
○ Perpendicular to the surface
 Friction force
○ Due to a rough surface
○ Opposes motion
 Tension
○ Caused by a rope
Inertia
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Tendency of an object to resist a change in its
state of motion
 Two states of motion
○ Rest
○ Constant velocity
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Depends on the mass of the object
 Mass: the amount of matter in an object
 Matter: anything that has mass and takes up space
 Volume: the amount of space occupied by an object
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Does not depend on location
 If mass is constant then inertia is constant
Inertia Clips
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Inertia of football
 http://www.youtube.com/watch?v=1hZf7hcrt
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Our friend Bill Nye explains inertia
 http://www.youtube.com/watch?v=vm22U85
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Magic Trick
Chalk in the tube
 Is it reasonable to say you can pull a
tablecloth and keep the dishes on the
table? Why? What would need to
happen?
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Bowling
What happens when you go bowling?
Does the ball slow down? What about
when you play kick ball? What is the
difference? Why?
 Let’s try it!
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Newton’s First Law
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Objects at rest tend to stay at rest and
objects in motion tend to stay in motion,
unless acted on by an external force.
 Just like our chalk and our bowling ball.
Julius Sumner Miller Time!
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http://www.youtube.com/watch?v=Kx2yq
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Space
How do objects move in space?
 How do we get them to move then?
 What would happen if we didn’t?
 Has anyone seen the movie “Gravity?”
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Seatbelts
What is the purpose of seatbelts? Why
are they designed the way they are?
How does this relate to physics and
Newton’s first law?
 Write a one paragraph letter to a
politician explaining why they should not
abolish seatbelt laws. Use physics to
back your argument.
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