Circular Motion Lab with Hanging Mass - Trying To Find Centripetal Force

[albert4united]

Sorry if this is posted in the wrong area, I am relatively new.

Circular Motion Lab is set up like this to study circular motion:

http://docs.google.com/viewer?a=v&q=cache:lG3nvirsnOYJ:www.hwscience.com/Physics/regphysics/Lab%2520Handouts/Circ.%2520motion%2520LAB.pdf+circular+motion+hanging+mass&hl=en&gl=ca&sig=AHIEtbTBHCVNZxCFmkJyfcwpOLkbKJl59w

Rubber stopper is secured to string .4m long, and is spun horizontally and achieves period of 0.56275s. The hanging mass is 0.03kg. The mass of the stopper is unknown.

I figured out that Centripetal velocity is 4.466m/s.

The vertical forces is Fnet = Ft - Fg

Ft= Fnet + Fg
Ft = m(a + g)
Ft= 0.03 (9.81)
Ft= 0.2943

The horizontal forces are Fc = Ft
Fc= 0.2943 N !

Is this done RIGHT to FIND the centripetal FORCE of the rubber STOPPER?
Please explain if I am wrong...

 

[Delphi51]

(hint: the radius of the circle made
by the stopper ≠ the length of the string but the angle will cancel out if you do the calculations correctly)

You must consider the angle of droop in your force diagram. Tension is certainly not a vertical force - it is PARTLY vertical and partly horizontal. You'll have sin A and cos A in your expressions when you separate T into horizontal and vertical parts.