TomLikesPhysics Group Title r(t)=(2t, wt, 4t) in cylindric coordinates. How do I find v(t)? one year ago one year ago

1. TuringTest Group Title

w is omega?

2. TomLikesPhysics Group Title

Yes

3. TuringTest Group Title

I can't see how it is anything other than just differentiating wrt t

4. TomLikesPhysics Group Title

I think the problem is that the unit vectors in cylindric coordinates also vary with time so it is not just v(t)=(2,w,4)

5. TuringTest Group Title

so the directions here are$\hat r,\hat\theta,\hat z$I suppose, eh?

6. TomLikesPhysics Group Title

right

7. TuringTest Group Title

8. TomLikesPhysics Group Title

No, however I just computed v(t)=(2, 2t*w, 4) but I don´t know if is correct or not.

9. TomLikesPhysics Group Title

I also have no clue how I could ask wolfram alpha to check that.

10. TomLikesPhysics Group Title

I used this formula but I am not entirely sure if this formula fits that problem.

11. TuringTest Group Title

I have never seen that formula, so I can't verify it...

12. TomLikesPhysics Group Title

I thought this is a "simple" problem.^^

13. TuringTest Group Title

http://www.maths.ox.ac.uk/system/files/coursematerial/2012/1115/77/CylCoords.pdf that formula you have seems to be right, though I can't seem to see where they get the extra rho from

14. TomLikesPhysics Group Title

The extra rho comes from the derevative of the unit vector e in the direction of phi.

15. TuringTest Group Title

ahh, okay, I had to read that sheet a but closer to get it thanks!

16. TomLikesPhysics Group Title

No problem, you´re welcome.