NEET Physics Hookes Law and Youngs Modulus MCQs Set A

Question. If the length of a wire is reduced to half, then it can hold the
(a) same load
(b) one fourth load
(c) half load
(d) double load

Answer: A

Question.  The Young’s modulus of a perfectly rigid body is
(a) infinity
(b) zero
(c) unity
(d) some finite non-zero constant

Answer: A

Question.  According to Hooke’s law of elasticity, if stress is increased, then the ratio of stress to strain
(a) remains constant
(b) increases
(c) becomes zero
(d) decreases

Answer: A

Question. The restoring force per unit area is known as
(a) stress
(b) plasticity
(c) elasticity
(d) strain

Answer: A

Question.  In magnitude hydraulic stress is equal to
(a) hydraulic pressure
(b) hydraulic strain
(c) hydraulic force
(d) restoring force

Answer: A

Question.  Substances which can be stretched to cause large strains are called
(a) elastomer
(b) plastic
(c) ductile
(d) brittle

Answer: A

Question. The reason for the change in shape of a regular body is
(a) shearing strain
(b) metallic strain
(c) volume stress
(d) longitudinal strain

Answer: A

Question.  Longidudinal stress depends on
(a) area
(b) length
(c) volume
(d) mass

Answer: A

Question. Which of the following affects the elasticity of a substance?
All of the above
(a) All of the above
(b) Impurity in substance
(c) Change in temperature
(d) Hammering and annealing

Answer: A

Question.  If the load is increased beyond the _______ point, the strain increases rapidly for even a small change in the stress.
(a) yield point
(b) fracture point
(c) elastic point
(d) plastic point

Answer: A

Question. Which of the following types of stress causes no change in shape?
(a) hydraulic stress
(b) none of these
(c) compressive stress
(d) oblique stress

Answer: A

Question.  A vertical metal cylinder of radius 2 cm and length 2 m is fixed at the lower end and a load of 100 kg is put on it. Find the strain. [Youn's modulus of the metal = 2 × 10¹¹ N/m²]
(a) 4 × 10^–6
(b) 3 × 10^–8
(c) 2 × 10^–9
(d) 6 × 10^–8

Answer: A

Question. If the ratio of radii of two wires of same material is 3 : 1 and ratio of their lengths is 5 : 1, then the ratio of the normal forces that will produce the same extension in the length of two wires is
(a) 1 : 1
(b) 1 : 4
(c) 4 : 1
(d) 2 : 1

Answer: A

Question.  Two wires of equal lengths are made of the same material. Wire A has a diameter that is twice as that of wire B. If identical weights are suspended from the ends of these wires, the increase in length is
(a) one-fourth for wire A as for wire B
(b) half for wire A as for wire B
(c) twice for wire A as for wire B
(d) four times for wire A as for wire B

Answer: A

Question.  Two persons pull a rope towards themselves. Each person exerts a force of 100 N on the rope. Find the Young's modulus of the material of the rope if it extends in length by 1 cm. Original length of the rope = 2 m and the aea of cross-section = 2 cm²
(a) 10⁸ N/m²
(b) 10⁶ N/m²
(c) 10⁷ N/m²
(d) None of these

Answer: A

Question. If stress/strain is x in eastic region and y in the region of yield, then
(a) x > y
(c) x = 2 y
(d) x = y

Answer: D

Question.  What per cent of length of wire increases by applying a stress of 1 kg weight/mm² on it? (Y = 1 × 10¹¹ N/m² and 1 kg weight = 9.8 newton)
(a) 0.0098%
(b) 0.0078%
(c) 0.0067%
(d) 0.0088%

Answer: A

Question. An elevator cable is to have a maximum stress of 7 × 10⁷ N/m² to allow for appropriate safety factors. Its maximum upwardacceleratiom is 1.5 m/s². If the cable has to support the total weight of 2000 kg of a loaded elevator, the area of cross– section of the cable should be
(a) 3.28 cm²
(b) 0.328 cm²
(c) 2.38 cm²
(d) 8.23 cm²

Answer: A

Question. To break a wire, a force of 10⁶ N/m² is required. If the density of the material is 3 × 10³ kg/m³, then the length of the wire which will break by its own weight will be
(a) 34 m
(b) 30 m
(c) 300 m
(d) 3 m

Answer: A

Question. A rubber cord catapult has cross-sectional area 25 mm² and,initial length of rubber cord is 10 cm. It is stretched to 5 cm and then released to project a missile of mass 5 gm. Taking Y_rubber = 5 × 10⁸ N/m². Velocity of projected missile is
(a) 250 ms^–1
(b) 20 ms^–1
(c) 100 ms^–1
(d) 200 ms^–1

Answer: A

Question.  A metallic rod breaks when strain produced is 0.2%. The Young’s modulus of the material of the rod is 7 × 10⁹ N/m². What should be its area of cross-section to support a load of 10⁴ N ?
(a) 7.1 × 10^–4 m²
(b) 7.1 × 10^–8 m²
(c) 7.1 × 10^–6 m²
(d) 7.1 × 10^–2 m²

Answer: A

Question.  A steel wire of original length 1 m and cross-sectional area 4.00 mm² is clamped at the two ends so that it lies horizontally and without tension. If a load of 2.16 kg is suspended from the middle point of the wire, what would be its vertical depression?
Y of the steel - 2.0 × 10¹¹N/m². Take g = 10 m/s²
(a) 1.5 cm
(b) 2.8 cm
(c) 3.2 cm
(d) 4.1 cm

Answer: A

Question. When forces are applied on a body such that it is still in static equilibrium, then the extent to which the body gets deformed, depends on
(a) Both
(b) nature of the material
(c) magnitude of deforming force
(d) None of these

Answer: A

Question. Two wires A and B of same material and of equal length with the radii in the ratio 1 : 2 are subjected to identical loads. If the length of A increases by 8 mm, then the increase in length of B is
(a) 2 mm
(b) 4 mm
(c) 16 mm
(d) 8 mm

Answer: A

Question. The length of an elastic string is a metre when the longitudinal tension is 4 N and b metre when the longitudinal tension is 5 N. The length of the string in metre when the longitudinal tension is 9 N is
(a) 5b – 4a
(b) a – b
(c) 4a – 3b
(d) 3a – 3b

Answer: A

Question. A steel wire of length l and cross section area A is stretched by 1 cm under a given load. When the same load is applied to another steel wire of double its length and half of its cross section area, the amount of stretching (extension) is
(a) 4 cm
(b) 1.5 cm
(c) 2 cm
(d) 0.5 cm

Answer: A

Question. Two wires are made of the same material and have the same volume. However wire 1 has cross-sectional area A and wire 2 has cross sectional area 9A. If the length of wire 1 increases by Dx on applying force F, how much force is needed to stretch wire 2 by the same amount?
(a) 81 F
(b) 64 F
(c) 25 F
(d) 16 F

Answer: A

Question.  What is the minimum diameter of a brass rod if it is to support a 400N load without exceeding the elastic limit ? Assume that the stress for the elastic limit is 379 MPa.
(a) 1.16 mm
(b) 2.32 mm
(c) 0.16 mm
(d) 1.35 mm

Answer: A

Question. The elastic limit of steel is 8 × 10⁸ N/m² and its Young's modulus 2 × 10¹¹ N/m². Find the maximum elongation of a half-meter steel wire that can be given without exceeding the elastic limit
(a) 2 mm
(b) 4 mm
(c) 5 mm
(d) 6 mm

Answer: A

Question.  A steel wire and a copper wire of equal length and equalcross-sectional area are joined end to end and thecombination is subjected to a tension. Find the ratio ofthe stresses developed in the two wires and Y of steel = 2 × 10¹¹ N/m². Y of copper = 1.3 × 10¹¹ N/m².
(a) 1
(b) 3
(c) 5
(d) 7

Answer: A

Question. A steel wire of cross-sectional area 3 × 1^0–6 m² can withstand a maximum strain of 10–3. Young's modulus of steel is 2 × 10¹¹ N/m² . The maximum mass the wire can hold is:
(a) 100 kg
(b) 80 kg
(c) 60 kg
(d) 40 kg

Answer: A

Question. A structural steel rod has a radius of 10 mm and length of1.0 m. A 100 kN force stretches it along its length. Young’smodulus of structural steel is 2 × 10¹¹ Nm^–2. The percentage strain is about
(a) 0.16%
(b) 0.32%
(c) 0.08%
(d) 0.24%

Answer: A