DO NOW (BRAIN POP) page 50/52

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DO NOW (BRAIN POP) page 50/52

• WRITE THE QUESTIONS AND THE ANSWERS
• What is the difference between ROTATION and
  REVOLUTION?
• Why do people not fall off carnival rides when it
  tips vertically?
• hinthint page 122-123 AND page 126 of the
  TEXTBOOOK

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CIRCULAR MOTION
PAGE 51 OF YOUR NOTEBOOK CORNELL NOTES
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ROTATION AND REVOLUTION

• Rotation is a spin about an axis located within
  the body.
• Revolution is movement around an axis outside the
  body
• Ex. A wheel rotates its rim revolves

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Rotating or Revolving?
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Rotating or Revolving?
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Rotating or Revolving?
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Rotating or Revolving?
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Rotating or Revolving?
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Rotating or Revolving?
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Rotating or Revolving?
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Rotating or Revolving?
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LINEAR SPEED

• Linear speed is the distance moved per unit of
  time
• Linear speed is greater on the outer edge of a
  rotating object than it is closer to its axis
• For circular motion we use the terms linear speed
  and tangential speed interchangeably.

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TANGENTIAL SPEED

• Tangential speed is the speed of something moving
  along a circular path
• The direction of motion is always tangent to the
  circle
• Depends on the rotational speed and the distance
  of the axis of rotation.

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Rotational speed

• Sometimes called angular speed is the number of
  rotations per unit of time, or how fast the angle
  changes.
• Commonly expressed as RPM, revolutions per
  minute.
• hinthint Figure 9.3 on page 124 (ladybugs)
• Examples
• The "second" hand of a conventional analogue
  clock rotates at 1 rpm.
• A washing machine drum may rotate at 500 to 2000
  rpm (833 Hz) during the spin cycles.
• Automobile Engines are usually operated at around
  2500 rpm (41 Hz), with the minimum speed usually
  around 1000 rpm (16 Hz)
• Audio CD players read their discs at a constant
  150 kB/s and thus must vary the disc's rotational
  speed from around 500 rpm (actually 8 Hz), when
  reading at the innermost edge, to 200 rpm
  (actually 3.5 Hz) at the outer edge

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Relationship between Tangential and Rotational
Speed

• Tangential Speed is directly proportional to the
  rotational speed and the radial distance from the
  axis of rotation.
• Tangential speed radial distance X rotational
  speed
• v r?

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• At the center of a rotating platform, right at
  its axis, you have no tangential speed, but you
  do have rotational speed.
• As you move away from the center, you move faster
  and increase your tangential speed while your
  rotational speed stays the same.
• In a rigidly rotating system all parts have the
  same rotational speed, but the linear or
  rotational speed varies.

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Problem 1

• The radius of a CD in a computer is 0.06 m. If a
  microbe riding on the discs rim has a tangential
  speed of 1.88 m/s. What is the discs angular
  speed?

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Problem 2

• During the spin cycle of a washing machine, the
  clothes stick to the outer wall of the barrel as
  it spins at a rate as high as 1800 revolutions
  per minute. The radius of the barrel is 26 cm.
• Determine the speed of the clothes (in m/s) which
  are located on the wall of the spin barrel.

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Problem 3

• A manufacturer of CD-ROM drives claims that the
  player can spin the disc as frequently as 1200
  revolutions per minute.
• If spinning at this rate, what is the speed of
  the outer row of data on the disc this row is
  located 5.6 cm from the center of the disc?

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VENN DIAGRAM (REVOLUTION VS ROTATION) PAGE 50
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Introduction to Centripetal Acceleration

• Centripetal acceleration is the
• acceleration that is directed towards the
• center of a circular path.

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Activity- Circular Motion

• Rotate marble in aluminum pan and answer the
  following questions in your notebook.
• Is the marble revolving or rotating around the
  pan?
• What is causing it to move around the outer wall
  of the pan?
• What determines how fast it will go?
• Which of Newtons Laws apply?
• What forced are acting on the marble and the pan?
• Predict how the marble would move if released
  from the pan?