Motion in a Straight Line

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Motion in a Straight Line
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Measurement of Speed

• Distance a scalar quantity measured in meters
• Total distance the sum of the all changes in
  position
• Time an interval of change measured in seconds
• Position Separation between the object and the
  reference point

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Types of Speed

• Rest no change in motion
• Instantaneous the current speed of an object at
  a point of time
• Average two ways to determine the mean
  movement
• Total distance / Total time
• Sum of the individual speeds / number of speed
  measurements
• Speed is a scalar quanity

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Velocity

• Displacement the change in position based on
  distance and Direction
• Velocity is the change in Distance per unit
  time with a specific direction
• Velocity is a vector quantity
• Velocity also has the following conditions
• Rest
• Average
• Instantaneous

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Sample Problem 1

• If a car is traveling at an average speed of 60
  meters per second, how long does it take to
  travel 12 meters?
• Formula v d/t
• Substitution of units 60 m/s 12m / t
• Solution t 12m / 60m/s
• t .2 s

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Describe motion in a straight line
Which car has the greatest velocity?
BLUE
Which car has a constant velocity?
RED
RED and GREEN
Which 2 cars have the same average velocity?
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Sample Problem 2

• If a car is traveling at an average speed of 24
  meters per second for 3 secs, and 48 meters per
  second for 3 seconds. What is the average speed
  for the 1st 3 seconds and for the entire 6
  seconds?
• Formula V V1 V2
• 2
• Substitution of units V 24m/s48m/s
• 2
• Solution V 64 m/s /2 32
  m/s

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Sample Problem 3

• If a car is traveling at an average speed of 24
  meters per second for 3 secs, and 48 meters per
  second for 3 seconds. What is the average speed
  for the 1st 3 seconds and for the entire 6
  seconds?
• Formula V V1 V2
• 2
• Substitution of units V 24m/s48m/s
• 2
• Solution V 64 m/s /2 32
  m/s

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Sample Problem 4

• A train travels between the 100 meter marker and
  the 250 meter marker in 10 seconds. What is the
  trains average speed?
• Formula V d/t
• Substitution of unitsV 150m / 10s
• V 15 m/s

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Summary

• Speed is based on position change relative to the
  origin
• Scalar and Vectors quantities are used to
  describe motion
• Calculations must include formula, substitution
  of proper units, and final solution in the MKS
  system.