A variable-speed motor is rigidly attached to a beam BC. When the speed of the motor is le...

A variable-speed motor is rigidly attached to a beam BC. When the speed of the motor is less than 600 rpm or more than 1200 rpm. a small object placed at A is observed to remain in contact withthe beam. For speeds between 600 and 1200 rpm the object is observed to “dance” and actually to lose contact with the beam. Determine the speed at which resonance will occur.