Period of circular motion given centrifugal force and radius

[blackice552]

1. Homework Statement :
A body of mass 81.7g is moving in a circular path of radius 0.65m. If we calculate the centrifugal force on it to have a magnitude of 0.35N, what is the period of revolution? (2 decimals, UNITS!)(p = 3.14)


2. Homework Equations :
I'm given the following equations:
a = v^2/r
v = Circumference/Period = 2pi/T
a = 4pi^2r/T^2
F = Mg
F = ma
3. The Attempt at a Solution :
I took .35 = mv^2/r so .35 = 81.7v^2/.65 so v = .5276
then I took T = 2pir/v so T = 2pi(.65)/.5276 so T =7.736

I got this wrong when I entered it. I may have rounded wrong at the end or didn't do it right in the first place Any help would be appreciated.

 

[andrevdh]

The supplied mass is in grams.

 

[blackice552]

so I would divide the mass by 1000 then do what i did?

 

[Kurdt]

Seems that way. Always take note of the units in questions and remember that standard formula are for SI units.

 

[andrevdh]

Yes. The S.I. unit of mass is kilograms.