question_answer 24)

                  A uniform metallic rod rotates about its perpendicular bisector with constant angular speed. If it is heated uniformly to raise its temperature slightly.                 (a) its speed of rotation increases.                 (b) its speed of rotation decreases.                 (c) its speed of rotation remains same.                 (d) its speed increases because its moment of inertia increases.                

Answer:

                  (b) When rod is heated, it expands and hence moment of inertia about its perpendicular bisector increases. According to the law of conservation of angular momentum, its angular speed decreases.