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Q & A: Rotational and Circular Motion

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Most recent answer: 10/22/2007
Q:
Could you please tell me the differences between, Rotational motion and Circular Motion. Can you give examples for each of them. Thank you.
- Jason Pfautz
Indiana, Pa, USA
A:
Jason -

For something to be 'circular motion,' it just has to move in a circle. For example, a toy train on a circular track has circular motion. For something to have 'rotational motion,' it has to actually have something that it's rotating around (called an axis). In general, a toy train on a track does not have an axis that it's rotating around, so it would not have rotational motion. A wheel on a car, however, rotates around the car's axle, so it does have rotational motion. For this example, if you were to pick a single point on the edge of the wheel, you could also say that it has circular motion.

-Tamara

(published on 10/22/2007)

Follow-Up #1: semantics

Q:
In circular motion for eg toy train is moving in circular path, we can consider axis passing through that center of the circle and perpendicular to the plane, then why it is not a rotational motion
- arun maheshwari (age 16)
ratlam
A:
Sure, you could say it is. I guess Tamara wanted to save the word rotational for cases where some rigid body rotated about its center of mass, without experiencing forces from something else, like the track. Whichever way you decide to use the words, we aren't confused about what is going on physically.

Mike W.


(published on 10/22/2007)

Follow-up on this answer.