A test mass of mass m2\displaystyle \frac{m}{2}2m is attached to a whirling string and moves in a horizontal circular path of radius 3r3r3r. The mass completes f f\,f revolutions each second.
What is the kinetic energy of the mass?
3π2mf2r23\pi^2 m f^2 r^23π2mf2r2
9π2mf2r29\pi^2 m f^2 r^29π2mf2r2
18π2mf2r218\pi^2 m f^2 r^218π2mf2r2
36π2mf2r236\pi^2 m f^2 r^236π2mf2r2
