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.

 

[kerimek]

Thank you for sharing your findings from the Circular Motion Lab. It appears that you have correctly calculated the centripetal velocity and identified the vertical and horizontal forces involved in the motion of the rubber stopper.

To answer your question, yes, your approach to finding the centripetal force of the rubber stopper is correct. The centripetal force is the net force acting towards the center of the circular motion, and in this case, it is equal to the tension force in the string (Ft). This is because the only horizontal force acting on the stopper is the tension force, and it is responsible for keeping the stopper moving in a circular path.

One suggestion for improvement would be to include the mass of the rubber stopper in your calculations. This can be done by using the equation Ft = mv^2/r, where m is the mass of the stopper and r is the radius of the circular motion. This will give you a more accurate value for the centripetal force.

Overall, your approach to finding the centripetal force is correct. Keep up the good work in your scientific studies!