A yo-yo rests on the floor (the static friction coefficient with the floor is μ). The inner (shaded)
portion of the yo-yo has a radius R1, the two outer disks have radii R2. A string is wrapped around
the inner part. Someone pulls on the string at an angle α (see sketch). The “pull” is very gentle and
carefully increased until the yo-yo starts to roll. Try it at Home; it’s Fun! You can watch the
demo on PIVoT! For whatangles of α will the yo-yo roll to the left and for what angles to the
right?

Question