CBSE Class 12 Physics Solids and Fluids Solved Problems

CBSE Class 12 Physics Solids and Fluids Solved Problems. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

Ex.1. A light rod of length 200 cm is suspended from the ceiling horizontally by means of two vertical wires of equal length tied to its ends. One of the wires is made of steel and is of cross-section 0.1 sq cm and the other is of brass of cross-section 0.2 sq cm. Find the position along the rod at which a weight may be hung to produce (a) equal stresses in both wires and (b) equal strains in both wires. (Ybrass = 10 × 10¹¹ dynes/cm². Ysteel = 20 × 10¹¹ dynes/cm².

Ex.2. A steel wire of diameter 0.8 mm and length 1 m is clamped firmly at two points A and B which are 1 m apart and in the same horizontal plane. A body is hung from the middle point of the wire such that the middle point sags 1 cm lower from the original position. Calculate the mass of the body. Given
Young’s modulus of the material of wire = 2 × 10¹² dynes/cm².

Sol.: Let the body be hung from the middle point C so that it sags through 1 cm to the point D as shown in
the figure

Ex.3. A rod AD, consisting of three segments AB, BC and CD joined together, is hanging vertically from a fixed support at A. The lengths of the segments are respectively 0.1 m, 0.2 m and 0.15 m. The crosssection of the rod is uniformly equal to 10^–4 m². A weight of 10 kg is hung from D. Calculate the displacements of the points B, C and D using the data on Young’s moduli given below (neglect the weight of the rod). YAB = 2.5 × 10¹⁰ N/m², YBC = 4.0 × 10¹⁰ N/m² and YCD = 1.0 × 10¹⁰ N/m2.

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