A homogeneous steel rod of length L = 1.20 m, mass M = 6.40 kg has two balls, of negligible dimensions, each of mass m = 1.06kg welded at its ends. The rod rotates in a horizontal plane around around a frictionless axis vertical passing through the centre of gravity of the system. Its angular velocity at time t = 0 is = 39 revolutions/s; subjected to a constant friction moment on the axis, stops after 32 s. Calculate: a) the angular acceleration of the system; b) the moment of the friction forces acting on the axis of rotation; c) the number of laps completed in 32 s; d) the number of turns completed in 32 s, also by applying the Work- energy.

A homogeneous steel rod of length L = 1.20 m, mass M = 6.40 kg has two balls, of negligible dimensions, each of mass m = 1.06kg welded at its ends. The rod rotates in a horizontal plane around around a frictionless axis vertical passing through the centre of gravity of the system. Its angular velocity at time t = 0 is = 39 revolutions/s; subjected to a constant friction moment on the axis, stops after 32 s. Calculate: a) the angular acceleration of the system; b) the moment of the friction forces acting on the axis of rotation; c) the number of laps completed in 32 s; d) the number of turns completed in 32 s, also by applying the Work- energy.