The Need for Speed

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The Need for Speed

• Chapter 11 MOTION

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• How do you know that something has moved?

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• To know something has moved you have to compare
  it to something else
• Ex ball on table
• Relative to the Earth it is not moving
• Relative to the sun it is moving
• (67,062 miles per hour)

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I. Distance and Displacement

• A. Frame of Reference
• system of objects that are NOT moving with
  respect to each other

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• B. Relative motion movement in relation to a
  frame of reference
• ex. traveling on a train

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• C. Distance
• length of path between two points
• If I drive 50 miles northwest to St. Cloud to get
  home, what is my distance?

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• D. Displacement
• How far something has moved from the starting
  point and in what direction
• as the crow flies

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• 1. displaced how far it has moved from the
  beginning to the end and in what direction
• If I drive 50 miles southeast to Rogers in the
  morning and then 50 miles northwest to St. Cloud
  to get home, what is my displacement?

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• E. Combining displacement
• 1. Vector
• a quantity that has a direction associated with
  it
• Shown with arrows
• 2. Add displacements using vector addition

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• A car goes 5 km east, then 2 km west. What is the
  cars displacement?

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• A car goes 5 km east, then 2 km west. What is the
  cars displacement?
• 5km
• 2km
• The displacement is 3 km east

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• Do the activity on p. 330

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II. Speed

• A. How far something goes in a certain amount of
  time
• B. Book Definition ratio of the distance an
  object moves to the amount of time the object
  moves

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• C. velocity speed with a direction
• A plane is going 200 mph North. Another is going
  200 mph West. Do they have the same speed? Do
  they have the same velocity?

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• D. Average speed total distance
• total time
• E. instantaneous speed
• speed at a particular instant
• On the speedometer

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• F. SI unit meters / second

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• G. Example problems
• 1. What is the average speed of a runner who
  travels 100 m in 10 seconds?

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• 2. A cyclist rides 5 km in 15 minutes, 2 km in
  the next 10 minutes, and 13 km in the next 35
  minutes. What is the cyclists average speed?
• 3. If a car travels with an average speed of 50
  miles an hour for 30 minutes, how far does the
  go?

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III. Acceleration

• A. change in velocity of an object
• B. change in speed, direction or both
• C. acceleration
• final velocity initial velocity
• time

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• D. Formula
• See board

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F. Example problems

• 1. A car is at rest at a stoplight. Ten seconds
  later it is going 60 kilometers per hour. What is
  the cars acceleration?

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• 2. A biker is stopped at a stoplight. She
  accelerates to 10 m/s in 20 seconds. What is her
  acceleration?

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• 3.A car is going 50 mph and accelerates to 70 mph
  in 10 seconds. What is its acceleration?

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• E. SI Units
• meter/second/second
• m/s/s
• m/s2

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IV. Graphing Motion

• A. Graph is a visual representation of data.
• B. Easier to interpret data

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• C. Distance vs time graphs
• The slope shows ___________

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• C. Distance vs time graphs
• The slope shows ___________
• What is slope?
• Rise over run
• So in this case it is distance over time
• Distance over time is _______

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• D. Speed vs. time graph
• The slope is ___________
• Hint Rise over run

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• See overhead for sample graphs