so again, I'm updating my question:

The figure shows a mass M inside a tube bent in a circle of radius R=1.50 m. M can slide with negligible friction inside the tube. The tube rotates about a vertical axis passing through the center. The mass is in equilibrium at θ =43.5 degrees. Calculate the number of revolution the hoop makes in 10.0 s.
so I got 4.78

Now my problem is with this :
Calculate the linear speed of the mass at that equilibrium location.
(in m/s)

here is it's picture
http://i49.tinypic.com/2cr845u.jpg

susus - it's better to ask a follow-up question in the same thread as before, rather than starting a new thread. From that previous thread (here: https://www.askmehelpdesk.com/physics/mass-inside-tube-533066.html ), the linear speed of the mass is the tube rotates is:


v = r\omega


and for this problem


r = R\sin \theta


You already know \omega and \theta , so what's the problem?

I just did not know how to update the question

Next time, just reply in the 'answer box'. The 'reply' button has a limited number of characters, so, it might be better in all cases to use the 'answer box'.

OK I did it , thanks