Does the Inside of a Wheel Spin Faster than the Outer Diameter?

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Discussion Overview

The discussion revolves around whether the inside of a wheel spins faster than the outer diameter, exploring concepts related to rotational motion and the mechanics of gears. Participants examine definitions of speed in terms of distance covered and angular velocity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that the definition of "faster" is crucial, questioning whether it refers to linear distance per unit time or angular rotation per unit time.
  • One participant states that every part of the wheel rotates at the same angular velocity (\omega), but the tangential velocity (v_{tangential}) increases with radius, indicating that the outer part moves faster.
  • Another participant notes that the outer part of the wheel has a faster velocity than the inner part, supporting this with a suggestion to observe marked points on the wheel as it turns.
  • A participant seeks clarification on whether the outer point must move faster to synchronize with the inner point, which covers less distance in the same time frame.
  • One participant emphasizes that a point near the center of the wheel travels a shorter distance during one rotation compared to a point further out, leading to the conclusion that the outer point has greater speed.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of speed and how it applies to the inner and outer parts of the wheel. There is no consensus on the definitions or implications of the terms used.

Contextual Notes

Participants highlight the importance of precise definitions and the conditions under which the discussion is framed, particularly regarding the meaning of "faster" and the mechanics of gears.

Who May Find This Useful

This discussion may be useful for individuals interested in understanding the principles of rotational motion, the mechanics of gears, and the nuances of speed definitions in physics.

cinemacell
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Does an inside of a wheel spin faster than the outer diameter of the wheel?

Isn't this how gears work?
 
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cinemacell said:
Does an inside of a wheel spin faster than the outer diameter of the wheel?

Isn't this how gears work?

Welcome to Physics Forums.

Like many questions, the answer varies with precise definition of the terms. What you mean by "faster"? Is passing over more distance per unit time (like more meters per second)? Or is it rotation through bigger angle per second (degrees per second)?
 
At every part of the wheel, it is rotating at the same rate. i.e. \omega is constant every part of the wheel. We also have:
v_{tangential} = \omega r
where r is radius from centre of wheel, so yes, the outer part of the wheel is moving faster.

The principle behind gears is that high gears require a greater torque to turn, but then they move the main bicycle wheel further round per pedal.
 
cinemacell said:
Does an inside of a wheel spin faster than the outer diameter of the wheel?

Isn't this how gears work?

Actually the outside of a wheel has a faster velocity than the inside. You can see this by putting a mark or something on the inside and outside of a wheel and observing while it turns.

I tried to do a paragraph on gears, but I don't know enogh terminology with gears and such to explain it well.
 
@Fewmet
To try to more precisely define the terms within my question: I guess what I'm trying to ask whether the speed inside a circle travels faster in terms of distance covered.

@BruceW
Do you mean to say that in order for both inner point and outer point of the wheel to arrive at the same destination at the same time - the outer point located at the outer of the wheel has to move faster in order to 'catch up' or be in sync to the inner point - which moves less to cover the same distance travelled?

@Drakkith
I would love a layman's explanation on gears being a layman myself.


Many many thanks for the replies guys.
 
Think about it like this: to do one rotation, a point near the centre of the wheel travels a much smaller distance than a point further out. Both parts must do 1 rotation in the same amount of time because the wheel is rigid. Therefore the point further from the centre has a greater speed.
 

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