Mass on a rotating turntable problem.

[btbam91]

[PLAIN]http://img841.imageshack.us/img841/7913/314pw.jpg

I'm having a bit of trouble with this one.

So the FBD of the block.

In the y coordinates, the normal equals its weight

in the x coordinates, we have static friction to the left, and is there a force to the right? There as to be right, since it eventually begins translating radially?

Just looking for a little guidance, thanks!

 

[Delphi51]

From the point of view of the outside observer, a centripetal force is required to hold the mass in circular motion. This is provided by the force of friction. So you begin with Fc = Ff, put in the details and calculate the speed for which they are just equal.

 

[btbam91]

the speed of the turntable and the block or just equal?

omega*R?

 

[Delphi51]

Yes, the speed of the turntable omega*R.
Then you can go for the time to reach that speed.