1. The problem statement, all variables and given/known data A yo-yo roughly speaking consists of two round, uniform discs, sandwiched around a third smaller disc. A string is wound around the middle disc, and so the yo-yo may roll up and down as the string winds and unwinds. Consider such a yo-yo, with the two bigger discs having radius R = 4.00 cm and mass M = 30.0 g each; and the smaller disc in the middle having radius r = 0.700 cm and mass m = 5.00 g. The string is taken to be massless, and infinitely thin. a) What is the total moment of inertia of the yo-yo, around an axis going through the centre of the discs? Indicate both the algebraic expression and a number. b) The end of the string is now fastened to something at a fixed position (like a finger), and the yo-yo is let drop towards the floor. Identify the forces acting on the yo-yo, and for each, indicate whether they provide torque, work, impulse and/or acceleration to the yo-yo. c) What is the acceleration of the yo-yo downwards; what is its angular acceleration? How large is the string force? d) How big a fraction of the total kinetic energy goes into the rotating motion? 3. The attempt at a solution Can somebody check my solutions? a) ΣI= 1/2mr^2 + MR^2=4.812 kg*m^2 b) There are forces like force of gravity and string force gravity provides Work and acceleration string provides torque and impulse c) a=g= 9.80 m/s^2 Fg=2Mg=0.588 N Fg=mg=0.049 N τ=RFg=0.02352 τ=rFg=3.43*10^-4 α=Στ/ΣI=5.6 rad/s^2 Fs=mg/1-(mR^2/ΣI)= 0.388 N d) haven't solved this one yet, does anybody have an idea for how to solve this one?