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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

CIRCULAR MOTION *PAGE 51 OF YOUR NOTEBOOK *CORNELL NOTES

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

Rotating or Revolving?

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.

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.

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 (8–33 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

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 = rω

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.

Problem 1 The radius of a CD in a computer is 0.06 m. If a microbe riding on the disc’s rim has a tangential speed of 1.88 m/s. What is the disc’s angular speed?

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.

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?

VENN DIAGRAM (REVOLUTION VS ROTATION) PAGE 50

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

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 Newton’s Laws apply? • What forced are acting on the marble and the pan? • Predict how the marble would move if released from the pan?

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