Why does (dr/dt)*θ = 0 when deriving Velocity?

[LearninDaMath]

Homework Statement


A derivation of Instantaneous Velocity

Arc length = s = θ * r

ds/dt = d(θr)/dt = Instantaneous V

Product rule:

V$_{t}$ = (dθ/dt)*r + (dr/dt)*θ

V$_{t}$ = (dθ/dt)*r + 0

V$_{t}$ = ωr




Question:

Why does dr/dt*θ = 0 ?

 

[xlava]

Since r is constant, the rate of change of the radius with respect to time (or anything for that matter) is going to be 0.

 

[LearninDaMath]

ah makes perfect sense, thanks.

 

[xlava]

ah makes perfect sense, thanks.

No problem, sir. Good luck.