Centripetal force ball on a string lab

[Revengeance]

Homework Statement

So referring to this lab , http://static3.mbtfiles.co.uk/media...ureate/physics/824297/html/images/image12.pngIn this lab you are holding the plastic tube and twirling it to make the small mass spin in a circle. Keep in mind there is a mass on the bottom.

I have to create an expression for Fc with theta and radius.

Homework Equations

Fc = 4pi^2rf^2 * m

The Attempt at a Solution

Well from the FBD of the small mass, we know that FC = FT

and from the FBD of the mass at the bottom we know that FT=FG.

Therefore for the system, wouldn't FC = FG of the mass on the bottom?

As for the equation i am not really sure were to start, could someone help me out please.

 

[andrevdh]

The string attached tot the mass going in a circle is angled downwards a bit, that is the horizontal plane in which the mass is circling is a bit below the top of the tube. That is the theta that is mentioned. Best to draw a diagram and post it.

 

[Revengeance]

so i know the lab looks something like this, and the Fg of the small mass will cancel out the fty in the tension, therefore ftx controlling the motion.

 

[andrevdh]

Yes, the x component provides the centripetal force.