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chart2006
Feb24-09, 10:29 PM
1. The problem statement, all variables and given/known data

The two-dimensional motion of a particle is defined by the relationship r = \frac {1}{sin\theta - cos\theta} and tan\theta = 1 + \frac {1}{t^2} , where r and \theta are expressed in meters and radians, respectively, and t is expressed in seconds. Determine (a) the magnitudes of velocity and acceleration at any instant, (b) the radius of curvature of the path.


2. Relevant equations

r = \frac {1}{sin\theta - cos\theta}


tan\theta = 1 + \frac {1}{t^2}



3. The attempt at a solution

I've made a few attempts but they seem way more complicated than the problem should be I think. I'm assuming I need to solve tan\theta for \theta . Once i've done that I figure I'd need to differentiate both r and \theta to find \dot{r}, \ddot{r}, \dot{\theta}, \ddot{\theta}.

I don't know if I'm on the correct route but any help would be appreciated. thanks!

gabbagabbahey
Feb25-09, 12:51 AM
I've made a few attempts but they seem way more complicated than the problem should be I think. I'm assuming I need to solve tan\theta for \theta .

Tangent is not a one-to-one function, so that's a bad idea.

Instead, draw a picture!:smile: I think you can find expressions for \sin\theta and \cos\theta in terms of t without actually solving for \theta first.....think 'right triangle':wink: