Chapter 5 Matter in Motion

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Chapter 5- Matter in Motion

• Section 1- Measuring Motion

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Objectives

• Identify the relationship between motion and a
  reference point
• Identify the 2 factors on which speed depends
• Determine the difference between speed and
  velocity
• Analyze the relationship of velocity to
  acceleration
• Interpret a graph showing acceleration

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Observing Motion

• To observe motion, you must observe the object in
  relation to another object that appears to be
  stationary.
• Reference point- The object that appears to stay
  in place
• Motion- An objects change in position over time
  when compared with a reference point

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Common Reference Points

• Common reference points are usually stationary,
  but can be moving
• Stationary Points
• Earths surface
• Buildings
• Mountains
• Moving Points
• Figure 1, page 108- hot air balloon in relation
  to a bird
• The earth itself

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Speed Depends on Distance Time

• Speed- The rate at which an object moves
• Speed depends upon 2 things
• Distance traveled
• Time taken to travel the distance
• SI unit for speed is meters per second (m/s)
• Others
• Miles/hr, km/hr, ft/sec

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Determining Average Speed

• Objects do not travel at a constant speed all the
  time
• Formula for average speed
• Average speed total distance total time

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Recognizing Speed on a Graph
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How Long Will It Take to Drive From Fayetteville
to Los Angeles?
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How Long Will It Take to Drive From Fayetteville
to Los Angeles?

• You are at Fayetteville AR.
• Turn left onto US-412 (Henri de Tonti Blvd) and
  go West for 4.1 miles to US-412
• Continue onto US-412 and go West for 24.5 miles
  to US-412 W
• Continue onto US-412 W (toll required for some
  segments) and go Northwest for 64.3 miles to I-44
  W (OK-66 W)

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How Long Will It Take to Drive From Fayetteville
to Los Angeles?

• Continue onto I-44 W (OK-66 W) (toll required for
  some segments) and go West for 101 miles to
  Turner Tpk
• Bear right on ramp to I-40 W (US-270 W) and merge
  with caution
• Continue on I-40 W (US-270 W) and go Northwest
  for 1200 miles to I-15 S

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How Long Will It Take to Drive From Fayetteville
to Los Angeles?

• Bear right onto I-15 S and go initially West,
  then generally Southwest for 58.5 miles to I-15 S
  (Ontario Frwy)
• Continue on I-15 S (Ontario Frwy) and go South
  for 13.3 miles to I-10 W (San Bernardino Frwy)
• Continue on I-10 W (San Bernardino Frwy) and go
  West for 40.2 miles to US-101 N (Santa Ana Frwy)
• You are at Los Angeles CA

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How Long Will It Take to Drive From Fayetteville
to Los Angeles?

• Estimated travel time 24 hours, 23 minutes for
  1544.4 miles of travel.
• Calculate the average speed for the entire trip.
• 1544.4 miles 24.38 hrs. 63.35 mph

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Does the Whole Equal the Sum of the Parts?

• Now calculate the following average speeds
• 133.7 mi in 2.22 hrs
• 74.0 mi in 1.67 hrs
• 168.3 mi in 3.35 hrs
• Are the average speeds the same?

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Velocity Direction Matters

• 2 birds leave the same place at the same time.
  They both fly at 10 km/h for 1 hr, 15 km/h for 30
  min, and 5 km/h for 1 hr. Why dont they end up
  in the same place?
• They had different velocities (flew in different
  directions)
• Velocity- The speed of an object in a particular
  direction
• Speed and Velocity are NOT the same thing

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Velocity Changes as Speed or Direction Changes

• Velocity is constant only if there is no change
  in speed or direction. Therefore, constant
  velocity is always along a straight line.
• Example
• If a bus speeds up from 15 m/s to 20 m/s
• If speed remains constant, but direction of
  travel changes

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Combining Velocities- Persons Resultant Velocity

• When you combine 2 velocities that are in the
  same direction, add the velocities together to
  find the resultant velocity
• When you combine 2 velocities that are in the
  opposite direction, subtract the smaller from the
  larger to find the resultant velocity. The
  resultant velocity is in the direction of the
  larger velocity

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Acceleration The Rate at Which Velocity Changes

• Acceleration- The rate at which velocity changes
• Acceleration is not just a change in velocity,
  but also how fast that change occurs
• To Calculate Acceleration
• (Final Velocity- Starting Velocity) Time it
  takes to change velocity

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Example

• Starting Velocity 0 mph
• Final Velocity 60 mph
• Time 5.2 seconds
• (FV-SV)T
• (60-0)5.2 11.54 m/h/s

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Examples of Acceleration
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Circular Motion Continuous Acceleration

• An object traveling in a circle is always
  changing its direction
• Therefore, its velocity is also constantly
  changing, so acceleration is occurring
• Centripetal Acceleration- Acceleration that
  occurs in a circular motion
• Example
• Windmill

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Recognizing Acceleration on a Graph
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Review

• What is Acceleration?
• Does a change in direction affect acceleration?
• What is a reference point?
• What 2 things must you know to determine speed?
• What is the difference between speed velocity?