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##\vec v## and ##\vec a## expressions - motion on an off center circle

Homework Statement
A particle moves along a circular trajectory, and its angular coordinate depends on ##q(t)=0,8t##. Considering ##Q## as the origin, find the expressions for velocity and acceleration in function of time, and also their radial and angular components.
Homework Equations
##\dot{r} = \dot{r} e_r + r \dot{\theta} e_\theta ##
##\ddot{x} = (\ddot{r}-r \dot{\theta}^2) e_r + (r \ddot{\theta}+2 \dot{r} \dot{\theta}) e_\theta##
Well, I tried decomposing velocity into its components on the radial and angular axis. But I have problems with the angles because in some parts of the trajectory the velocity is on the angular coordinate, but in other parts it isn't. I mean, I can't say ##V=V e_\theta## because it's not always like that. So I'm having problems finding out which trigonometric relationship should I use to be able to decompose it.

20190831_142328.jpg
 

Charles Link

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It's unclear how you worded the problem in the OP what ## q(t) ## is. The problem probably is somewhat routine, but I can't follow what ## q(t)=0,8t ## means.
 

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