Exams › JEE Advanced › Physics

A cylindrical wire of radius 1 mm and length 1 m (Young's modulus = 2 x 10¹¹ N/m², Poisson's ratio mu = pi/10) is stretched by a force of 100 N. What does its radius become?

1. 0.99998 mm
2. 0.99999 mm
3. 0.99997 mm
4. 0.99995 mm

Correct answer: 0.99995 mm

Solution

Longitudinal strain = 100/(pi*1e-6*2e11) = 1.59e-4; Delta r/r = -(pi/10)(1.59e-4) = -5e-5, so r = 0.99995 mm.

Related JEE Advanced Physics questions

• A steel wire is used to suspend an object with a specific gravity of ρ, and the fundamental frequency of transverse standing waves in the wire is 300 Hz. When the object is partially submerged in water such that half of its volume is underwater, what will the new fundamental frequency (in Hz) become?
• Two wires — one steel, one brass — are connected in series and support three equal masses (each of mass m) hanging from their lower ends, with the steel wire attached to the ceiling. The ratios L_steel/L_brass = a, r_steel/r_brass = b, and Y_steel/Y_brass = c. Find the ratio of the elongation of the steel wire to that of the brass wire.
• In Searle's experiment for measuring Young's modulus of elasticity of a wire, after applying each increment of load the experimenter waits for approximately two minutes before taking a reading. What is the primary reason for this waiting period?
• Two rods made of different materials are sandwiched between two rigid massive walls as shown. The cross-sectional area of both rods is A. Their Young's moduli are E1 and E2, their lengths are l1 and l2, and their coefficients of linear expansion are alpha1 and alpha2 respectively. When the system is heated through T degrees, which of the following statements is/are correct?
• Two wires A and B are made of the same material. The ratio of their lengths is L_A: L_B = 1: 2 and the ratio of their diameters is d_A: d_B = 2: 1. When the same force F is applied to each wire, find the ratio of the increase in length of wire A to that of wire B (delta_L_A: delta_L_B).
• Two metallic wires P and Q are made of the same material and have the same volume. Their cross-sectional areas are in the ratio 2:1. If the forces required to produce the same extension in both wires are F1 (for P) and F2 (for Q) respectively, find the ratio F1/F2.

⚔️ Practice JEE Advanced Physics free + battle 1v1 →