A spool of thin wire pivots on a shaft

[SereneKi]

Homework Statement

Pulley with Friction
A spool of thin wire pivots on a shaft, and there is friction. The wire is pulled by a hanging mass M of 1.30 kg. After falling a distance D= 1.7 m starting from rest, the mass has a speed of 0.065 m/s. Calculate the energy lost to friction during that time.
Inner radius, ri = 0.50 m
Outer radius, r0 = 0.65 m
Icm= 0.96 kg/m2.

The Attempt at a Solution

a=v^2/2*D -> a=0.0036
T=m(g-v^2/2*D) -> T=12.24
alpha=a/r0=(r0*T-Qf)/Icm -> Qf=7.951
theta=D/r0 ->2.62
Ef=theta*Qf -> Ef=20.83

what am I doing wrong?

 

[tiny-tim]

Hi SereneKi!

I don't understand the question …

is there a pulley and a spool?

between what surfaces is the friction?

what is the relevance of the outer radius of the spool?