PHY131H1S - Class 7

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PHY131H1S - Class 7

• Today
• Review for tomorrows test
• In tba, 600 730pm
• On Chapters 1-3, Error Analysis Mini-Document,
  and Sections 4.1 through 4.4.
• Bring a calculator and one 8.5x11 aid sheet
  which you prepare, double-sided

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• You drop a glass barometer from the top of
  McLennan Physical Labs. A short time later,
  before the barometer hits the ground, you drop a
  bottle of scotch. As they fall, the distance
  between the barometer and bottle
• decreases
• increases
• stays the same.

Niels Bohr
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Relative Motion

• Example 1 A passenger walks toward the front of
  the train at 5 m/s. The train is moving at 36
  m/s. What is the speed of the passenger relative
  to the ground?
• Example 2 Car A is traveling at 25.0 m/s E
  toward Bloor and Keele. Car B is traveling at
  15.8 m/s N toward Bloor and Keele. Just before
  they collide, what is the velocity of car A
  relative to car B?

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A particle moves from position 1 to position 2
during the interval ?t. Which vector shows the
particles average velocity?
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During which time interval is the particle
described by these position graphs at rest?

1. 01 s
2. 12 s
3. 23 s
4. 34 s

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A 50 g ball rolls off a table and lands 2 m from
the base of the table. A 100 g ball rolls off the
same table with the same speed. It lands at a
distance

1. less than 2 m from the base.
2. 2 m from the base.
3. greater than 2 m from the base.

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The Gaussian
68 of data between the dotted lines on the graph.
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Mean and Standard Deviation of a set of numbers

• Repeat the same measurement N times. You measure
  the values x1, x2, x3, , xN. In other words,
  you measure xi, where i is an index which ranges
  from 1 up to N.
• The estimated mean is

• The estimated standard deviation is

• You can estimate that s is the error in any
  individual measurement xi ?xi s.

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Propagation of Errors
z A x
?z A ?x
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Repeated Measurements

• Repeated n times
• Each individual measurement has an error of
  precision Dx

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Motion with Constant Accelerationanother useful
equation!
Does not contain si or sf !
Does not contain vfs !
Does not contain Dt !
Does not contain as! (..but it does require that
as is a constant.)
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Projectile Motion Example

• A car drives off a cliff of height d with speed
  v0.
• The ground is horizontal both at the top and
  bottom of the cliff.
• How far from the base of the cliff does the car
  land?

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Before Class 8 on Wednesday

• Test is tomorrow! tba, 600pm.
• On Chs. 1-3, Error Analysis, and Sections 4.1
  through 4.4.
• Bring a calculator and one 8.5x11 aid sheet
  which you prepare, double-sided
• By Wednesday, please finish reading Chapter 4
• Something to think about You are driving North
  Highway 427, on the smoothly curving part that
  will join to the Westbound 401. Your speedometer
  is constant at 115 km/hr. Your steering wheel is
  not rotating, but it is turned to the left to
  follow the curve of the highway. Are you
  accelerating? If so, in what direction?