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

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SUMMARY

The relationship between angular velocity (ω) and linear velocity (v) in circular motion is defined by the equation dθ/dt = v/r, where θ is the angle in radians, v is the linear velocity, and r is the radius of the circular path. The derivation shows that as the arc length (l) is related to the angle by the formula θ = l/r, differentiating this with respect to time leads to the conclusion that rω = v. This confirms that the angular velocity is directly proportional to the linear velocity when considering the radius of the circle.

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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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