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Circular motion

Circular motion. Day 1, 10/29/2013. Rotating – turning around an internal axis. Revolving Turning about an external axis. Linear speed, v How far you go in a certain amount of time Miles per hour, meters per second Rotational (angular) speed, ώ

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Circular motion

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  1. Circular motion Day 1, 10/29/2013

  2. Rotating – turning around an internal axis

  3. Revolving Turning about an external axis

  4. Linear speed, v How far you go in a certain amount of time Miles per hour, meters per second Rotational (angular) speed, ώ How many times you go around in a certain amount of time Revolutions per minute, rotations per hour, radians per second

  5. Which horse has a larger linear speed on a merry go round, one on the outside or one on the inside? Outside. Which horse has a greater rotational speed? Neither, all the horses complete the circle in the same amount of time. Tutorial on Circular motion http://www.youtube.com/watch?v=nb4VzvfkSN0

  6. The number of revolutions per second is called the frequency, f. Units are Hertz, Hz. The time it takes to go all the way around once is called the period, T. Units could be seconds, minutes, hours, years. Frequency is related to period by f = 1 / T

  7. What is the frequency of Earth’s rotation on its axis? Period, T = 24 hours = 86400 seconds f = 1 / T f = 1 / 86400 f = 1.16 x 10-5 Hz

  8. Remember Velocity = distance / time For circular motion, the distance traveled is all around the circle… the circumference. The circumference = 2pr So… v = 2pr / T

  9. Solve this! A disk with a radius of 0.25 m turns at 33 revolutions in one minute. What is the speed of a point along the outer edge? r = 0.25 m f = 33 rev/min X • = 0.55 rev/sec or Hz v = ? v = 2pr / T Could it be that v = 2pr(f)? v = 2p(0.25)(0.55) v = 0.864 m/s

  10. Uniform Circular Motion, UCM: moving in a circle with a constant speed. Question: Is there a constant velocity when an object moves in a circle with a constant speed? No, the direction changes, therefore the velocity changes. If the velocity changed, the object is actually ACCELERATING even while moving at the same speed.

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