3.1 Notes, Part B

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3.1 Notes, Part B
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Todays Objectives

• Calculate the average speed of an object.
• Explain the difference between speed and
  velocity.

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Speed

• Distance an object travels per unit of time
• Distance in meters
• Time in second
• Scalar quantity
• refers to "how fast an object is moving.

Distance
Speed
time
d

t
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Speed changing
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Speed

• SI unit for speed is
• m/s

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• Average speed total distance traveled divided
  by total travel time
• Km/hour
• Instantaneous speed speed at a single instant
  of time
• Speedometer measures this

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Example

• While on vacation, Lisa traveled a total distance
  of 440 miles. Her trip took 8 hours. What was her
  average speed?
• To compute her average speed, we simply divide
  the distance of travel by the time of travel.

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Velocity

• Speed and direction
• Vector quantity
• refers to "the rate at which an object changes
  its position.
• I traveled south at 60 mi/h to get to school
• Velocity changes if
• You change speed
• You change direction

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Average velocity

• Different from average speed

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Example 1

• Physics Teacher again, walked 12 m in 24 seconds
• Displacement 0 m

Average speed 0.50 m/s Average velocity 0 m/s
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Example 2

• Cross-country skier again
• Distance 420 m
• Displacement 140 m, right

Average speed 140 m/min Avg. velocity 46.7
m/min, right
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Example 3

• Football coach again,
• Distance 95 yds
• Displacement 55 yds, left

Average speed 9.5 yds/min Avg. velocity 5.5
yds /min, left
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In-class Assignment/Homework

• Finish 3.1 B Lecture Tutorial