A disc of radius a is rigidly attached at its circumference by two rods each of length 3a, two rods are always perpendicular to each other. The combination is suspended vertically from the free end of one rod (as shown in figure). It is swinging in the plane of the disc such that the centre of disc have velocity v. If mass of disc and each rod is m.

Question

G1 Physics · Accepted Answer

Write translation ΣF=Ma and rotation Στ about CM=I about CMα, together with the no-slip relation v of CM=ωR and a of CM=αR whenever pure rolling applies. Solving the equations for the shown geometry gives A: kinetic energy of disc = ½mV² + ½(ma²/2)(V/4a)²; C: kinetic energy of rod 1 = ½[m(3a)²/3](V/4a)²; D: total kinetic energy = sum of translational and rotational kinetic energies of the disc and both rods.