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magnetismman
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Question on Acceleration of Rotating Objects:
The Physics Textbook I have says that the Acceleration of a spinning object is the Pythagorean-theorum result of sides for Centripetal-Acceleration (toward the rotation center) and Tangential-Acceleration (perpendicular to Centripetal-Acceleration in the direction of movement). It seemed pretty straight-forward, until I got to calculating each. According to the book:
Centripetal-Acceleration – ac :
Is either:
(1) Tangential-Velocity squared, over radius OR
(2) Angular-Velocity squared, times radius.
Tangential Acceleration – at :
Radius * Angular-Acceleration.
The problem I think I've found is in the units for each.
For Centripetal-Acceleration:
Tangential-Velocity = radius * angular-velocity (meter-radians-per-second)
Radius is a base unit (meters)
...so Tangential-Velocity squared, over radius has the unit:
(radian-radian-meters-per-second-per-second)
Please note, I did get a “Domain of result may be larger” warning from my calculator.
For Tangential-Acceleration:
Angular-Acceleration = Angular-Velocity-Change per second (Radians-per-second-per-second)
Radius is a base unit (meters)
...so Radius times Angular-Acceleration has the unit:
(radian-meters-per-second-per-second)
How can the two be combined for a total rotational-acceleration if the units are different?
Centripetal-Acceleration (ac): (radians2*meters / second2)
Tangential-Acceleration (at): (radians*meters / second2)
Since the units are different, the combined acceleration would be in neither unit.
Is this a flaw in the theory?
Is this some flaw in my reasoning?
Thank you for your advice.
Information-Source: Cutnell&Johnson - 'Physics' 6th Edition (Chapter 8) – ISBN:0-471-15183-1
The Physics Textbook I have says that the Acceleration of a spinning object is the Pythagorean-theorum result of sides for Centripetal-Acceleration (toward the rotation center) and Tangential-Acceleration (perpendicular to Centripetal-Acceleration in the direction of movement). It seemed pretty straight-forward, until I got to calculating each. According to the book:
Centripetal-Acceleration – ac :
Is either:
(1) Tangential-Velocity squared, over radius OR
(2) Angular-Velocity squared, times radius.
Tangential Acceleration – at :
Radius * Angular-Acceleration.
The problem I think I've found is in the units for each.
For Centripetal-Acceleration:
Tangential-Velocity = radius * angular-velocity (meter-radians-per-second)
Radius is a base unit (meters)
...so Tangential-Velocity squared, over radius has the unit:
(radian-radian-meters-per-second-per-second)
Please note, I did get a “Domain of result may be larger” warning from my calculator.
For Tangential-Acceleration:
Angular-Acceleration = Angular-Velocity-Change per second (Radians-per-second-per-second)
Radius is a base unit (meters)
...so Radius times Angular-Acceleration has the unit:
(radian-meters-per-second-per-second)
How can the two be combined for a total rotational-acceleration if the units are different?
Centripetal-Acceleration (ac): (radians2*meters / second2)
Tangential-Acceleration (at): (radians*meters / second2)
Since the units are different, the combined acceleration would be in neither unit.
Is this a flaw in the theory?
Is this some flaw in my reasoning?
Thank you for your advice.
Information-Source: Cutnell&Johnson - 'Physics' 6th Edition (Chapter 8) – ISBN:0-471-15183-1
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