Question

The 1.4 kg, 40-cm-diameter disk in the figure below is spinning at 260 rpm. How much friction force must the brake apply to the rim to bring the disk to a halt in 4.5 s?

Answer 1

torque=momentinertia*ang acceleration

look up the momentInertia for a disk
ang acceleration=(260*2PI)/4.5

torque= frictionforce*radius