The centre of mass of the cylinder does not exactly coincide with its vertical axis.This causes the cylinder to vibrate slightly as it rotates. Between 1 = 230 s and 1=250 s, the angular acceleration of the cylinder decreases significantly and the cylinder vibrates with a greater amplitude. After 1 = 250 s, the amplitude of these vibrations decreases and the angular acceleration increases again. Suggest an explanation for the changes in amplitude of vibration and for the changes in angular acceleration.