Question

Two flywheels of negligible mass and different radii are bonded together and rotate about a common axis (see below). The smaller flywheel of radius 40 cm has a cord that has a pulling force of 60 N on it. What pulling force needs to be applied to the cord connecting the larger flywheel of radius 60 cm such that the combination does not rotate?

Answer 1

$$F_1r_1=F_2r_2\\(40)(60)=F_2(60)\\F_2=40\ N$$