How is dθ/dt related to v/r in circular motion?

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Homework Help Overview

The discussion revolves around the relationship between angular velocity (dθ/dt) and linear velocity (v) in the context of circular motion, specifically questioning how dθ/dt relates to the formula v/r.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the definitions of angular displacement and its relationship to arc length and radius. There is a discussion about whether the arc length must be in radians and the implications of radius values in the context of the formulas presented.

Discussion Status

Some participants have provided insights into the relationships between angular and linear quantities, while others are clarifying their understanding of the definitions involved. There appears to be a productive exchange of ideas, with some participants expressing newfound clarity on the concepts discussed.

Contextual Notes

Participants are navigating assumptions about the units of measurement for arc length and the implications of radius values in their calculations.

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Homework Statement

just a conceptual thing I don't quite understand..
how come dtheta/dt = v/r? I thought it was basically the same thing as v = r/t, but with radians..
thanks

Homework Equations


The Attempt at a Solution

 
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ω=dθ/dt

now θ is the angle of an arc of a circle of radius r and arc length l.

so θ=l/r

So ω=d/dt(l/r)

r doesn't change so
rω=dl/dt

and dl/dt=v

so rω=v
 


rock.freak667 said:
ω=dθ/dt

now θ is the angle of an arc of a circle of radius r and arc length l.

so θ=l/r

So ω=d/dt(l/r)

r doesn't change so
rω=dl/dt

and dl/dt=v

so rω=v

Hi, thanks a lot for the reply. Do we say θ=l/r because the arc length might not be in radians?

thanks
 


emyt said:
Hi, thanks a lot for the reply. Do we say θ=l/r because the arc length might not be in radians?

thanks

Are length is defined as l=rθ when θ is in radians.
 


rock.freak667 said:
Are length is defined as l=rθ when θ is in radians.

EDIT: oh never mind, I've got it.. I've somehow forgotten that a radius could be more than 1 unit :P thanks!
 

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