Find the angular frequency of torsional pendulum

[roxysnwbrd]

a disk (radius R = 1.0 m, mass = 2.0 kg) is suspended from a
pivot a distance d = 0.25 m above its center of mass. The angular frequency (in
rad/s) for small oscillations is approximately?

t=-k(theta)
w=(k/I)^1/2
unsure what the equation is for I?I don't know how to use the given values to find the information I need (K and I)

 

[rock.freak667]

Hi roxysnwbrd,

Firstly what you should do is draw a free body diagram of the mass slightly displaced at an angle θ.

Then split the weight in its components, one will be tangential to the disc.

Find the resultant torque on the mass and we can go from there.


EDIT: The ω in your relevant equations is for a torsional spring, which is not the case here.

To get I you need to get I for a disk.