Posted by mike on .
A mass m = 0.5 kg is hung from a pulley with moment of inertia I = 0.20kg⋅m2 and radius R = 10cm. There is friction in the pulley. The mass is dropped from rest, and after 2s it traveled 0.4m. What is the torque due to friction?

physics 209 
Elena,
s=at²/2 => a=2s/t²=2•0.4/2²=0.2 m/s²
The equation of the load motion
ma=mgT => T=m(ga)
The equation of the pulley motion
Iε=MM(fr)
M(fr) = MIε = TRIa/R=
=m(ga)R – Ia/R = ...