Re: Problem with a problem

["Van E. Neie" <ven@PHYSICS.PURDUE.EDU>]

"Harry L. Hightower" wrote:

>         How do you go about solving the following problem?
>         A thin rigid rod is rotating with a constant angular
> acceleration about an axis that passes perpendicularly
> through one of its ends. At one instant, the total
> acceleration vector (centripetal plus tangential) at the
> other end of the rod makes a 60.0 degree angle with
> respect to the rod and has a magnitude of 15.0 m/s/s.
> The rod has an angular speed of 2.00 rad/s at this
> instant. What is the rod's length?
>         I am probably making this harder than what it really is.
>
>                                            Thanks
>                                                    Harry

The acceleration vector a is composed of a(t) and a(r).   And a(t) = a
cos 60.  a(r) = (omega)^2 r.  Then you can write tan 60 = a(r)/a(t).
This  gives you an expression with r being the only unknown.   If I
didn't screw something up, I got 3.25 m


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