rotation help?

Question

this is part of the analysis for the lab
trial 1
radius=.4m
time=10secs
mass=.05kg
rotations=22
How do i calculate linear speed? is it (2*(PI)*r*#of rot) /t?

How do i calculate the centripetal force the object should have had based on the mass, linear velocity, and circle radius? i have no idea how to do this

Ho do i calculate the force needed to keep each mass going in a circle (the weight on the string). Show the calculation of the force for at least one test from each experiment? i have no idea again

thanks
does anyone know how to do th third one?

Answer 1

1. The linear tangential speed is
V=2 pi R N/t
N is the number of turns during time t

2. Fc=m ac (centripital acceleration)
ac= V^2/R

3. F=T/R
T=I A
I -moment of inertia (depends on the geometry of the mass in question?)
A - angular acceleration

If it is a weight on the string than I=mr^2
A= at/R

at = change of linear tangential velocity (speed) with respect to time.
at= V/t
F= I A/R
F= m R^2 (V/t) /R
F= m R V/ t