Consider two cylindrical rods of identical dimensions, one of rubber and the other of steel. Both the rods are fixed rigidly at one end to the roof. A mass M is attached to each of the free ends at the centre of the rods.

Options

A. Both the rods will elongate but there shall be no perceptible change in shape.
B. The steel rod will elongate and change shape but the rubber rod will only elongate.
C. The steel rod will elongate without any perceptible change in shape, but the rubber rod will elongate and the shape of the bottom edge will change to an ellipse.
D. The steel rod will elongate, without any perceptible change in shape, but the rubber rod will elongate with the shape of the bottom edge tapered to a tip at the centre.

Answer

D

Explanation

According to the diagram, the mass M is attached at te elongated. But due to different elastic properties of material, rubber rod will elongate with the shape of the bottom edge tapered to a tip at the centre.