31 + Interview Questions in GENERAL QA IN ELASTICITY Page 1 InterviewSolution

1.	A wire elongates by l mm when a load W is hanged from it. If the wire goes over a pulley and two weights W each are hung at the two ends, the elongation of the wire will be (in mm) (1) zero (2) l/2 (3) l (4) 2l
Answer» Correct option (3) l Explanation: In both the cases, the tension in the wire remains the same. So, elongation will be the same.

1.

A wire elongates by l mm when a load W is hanged from it. If the wire goes over a pulley and two weights W each are hung at the two ends, the elongation of the wire will be (in mm) (1) zero (2) l/2 (3) l (4) 2l

Answer»

Correct option (3) l

Explanation:

In both the cases, the tension in the wire remains the same. So, elongation will be the same.

2.	The property of metals whereby they could be drawn into thin wires beyond their elastic limit without breaking is (1) Ductility (2) Malleability (3) Elasticity (4) Hardness
Answer» (1) Ductility.

Discussion

3.	The possible value of Poisson’s ratio is (1) 0.9 (2) 0.8 (3) 0.4 (4) 1
Answer» The possible value of Poisson’s ratio is 0.4 .

Discussion

4.	A heavy mass is attached to a thin wire and is whirled in a vertical circle. The wire is most likely to break (1) When the mass is at the lowest point (2) When mass is at the highest point (3) When wire is horizontal (4) When mass is at an angle of cos-1 (1/√2) from upward vertical
Answer» (1) When the mass is at the lowest point

Discussion

5.	The breaking stress of a wire depends on (1) Material of a wire (2) Shape of cross section (3) Length of the wire (4) Radius of the wire
Answer» (1) Material of a wire

Discussion

6.	Steel is preferred for making springs over copper because (1) Young's modulus of steel is more than that of copper ( 2) Steel is cheaper (3) Young's modulus of copper is more ( 4) Steel is less likely to be oxidized
Answer» (1) Young's modulus of steel is more than that of copper

Discussion

7.	Steel is preferred for making springs over copper because (1) Young's modulus of steel is more than that of copper (2) Steel is cheaper (3) Young's modulus of copper is more (4) Steel is less likely to be oxidized
Answer» (1) Young's modulus of steel is more than that of copper .

Discussion

8.	The following four wires are made of the same material subjected to same force arrange them with their elongations in ascending order(a) l = 50cm and r = 0.5mm (b) l = 100cm and r = 1mm (c) l = 200cm and r = 2mm (d) l = 300cm and r = 3mm (1) a, b, c, d (2) c, d, a, b (3) a, d, c, b (4) d, c, b, a
Answer» (4) d, c, b, a.

Discussion

9.	(A): Identical springs of steel and copper are equally stretched. More work will be done on the steel spring. (R): Steel is more elastic than copper. (1) Both (A) and (R) are true and (R) is the correct explanation of (A) (2) Both (A) and (R) are true and (R) is not the correct explanation of (A) (3) (A) is true but (R) is false (4) (A) is false but (R) is true
Answer» (1) Both (A) and (R) are true and (R) is the correct explanation of (A)

Discussion

10.	A copper wire of negligible mass, length 1 m and cross-sectional area 10–6 m2 is kept on a smooth horizontal table with one end fixed. A ball of mass 1 kg is attached to the other end. The wire and the ball are rotating with an angular velocity of 20 rad/s. If the elongation in the wire is 10–3 m, obtain the Young’s modulus of copper. If on increasing the angular velocity to 100 rad/s, the wire breaks down, obtain the breaking stress.
Answer» The stretching force developed in the wire due to rotation of the ball is F = mrω² = 1 × 1 × (20)² = 400 N Stress in the wire = F/A = 400/10^-6 N/m² Strain in the wire = 10^-3/1 = 10^-3 Young’s modulus, Y = Stress/Strain = 400/10^-6x 10^-3 = 4 × 10¹¹ N/m² Breaking stress = 1 x 1 x(100)²/10^-6 = 1010 N/m².

10.

A copper wire of negligible mass, length 1 m and cross-sectional area 10–6 m2 is kept on a smooth horizontal table with one end fixed. A ball of mass 1 kg is attached to the other end. The wire and the ball are rotating with an angular velocity of 20 rad/s. If the elongation in the wire is 10–3 m, obtain the Young’s modulus of copper. If on increasing the angular velocity to 100 rad/s, the wire breaks down, obtain the breaking stress.

Answer»

The stretching force developed in the wire due to rotation of the ball is

F = mrω² = 1 × 1 × (20)² = 400 N

Stress in the wire = F/A = 400/10^-6 N/m²

Strain in the wire = 10^-3/1 = 10^-3

Young’s modulus, Y = Stress/Strain = 400/10^-6x 10^-3

= 4 × 10¹¹ N/m²

Breaking stress = 1 x 1 x(100)²/10^-6 = 1010 N/m².

Discussion

11.	A body subjected to strain a number of times does not obey Hooke's law due to (1) Yield point (2) Breaking stress (3) Elastic fatigue (4) Permanent set
Answer» (3) Elastic fatigue

Discussion

12.	Assertion (A) : Ductile metals are used to prepare thin wires. Reason (R) : In the stress-strain curve of ductile metals, the length between the points representing elastic limit and breaking point is very small. (1) Both (A) and (R) are true and (R) is the correct explanation of (A) (2) Both (A) and (R) are true and (R) is not correct explanation of (A) (3) (A) is true but (R) is false. (4) (A) is false but (R) is true.
Answer» (3) (A) is true but (R) is false.

Discussion

13.	Match the following. List I List II(a) Spring constant (e) 1/2 (stress)2/Y(b) Tensile strength(f) Δp/ΔV/V(c) Bulk modulus (g) Breaking stress (d) Potential energy/ Unit volume(h) AY/L(1) a-h, b-g, c-f, d-e (2) a-g, b-h, c-e, d-f (3) a-e, b-h, c-f, d-g (4) a-h, b-e ,c-f, d-g
Answer» (1) a-h, b-g, c-f, d-e

Discussion

14.	Consider an ideal mono-atomic gas of volume at pressure P. The bulk modulus at constant temperature is (1) p/2 (2) P (3) γ P (4) PdP/dV
Answer» The bulk modulus at constant temperature is P.

Discussion

15.	Which of the following substances has the highest elasticity? (1) Rubber (2) Steel (3) Copper (4) Wood
Answer» Steel substances has the highest elasticity.

Discussion

16.	The modulus of elasticity is dimensionally equivalent to (1) Stress (2) Surface tension (3) Strain (4) Coefficient of viscosity
Answer» The modulus of elasticity is dimensionally equivalent to Stress.

Discussion

17.	The strain produced in the stretched spring is (1) Volume strain (2) Shearing strain (3) Tensile strain (4) None of the above
Answer» (2) Shearing strain

Discussion

18.	On all the six surfaces of a unit cube, equal tensile force of F is applied. The increase in length of each side will be (Y = Young's modulus, σ = Poisson’s ratio) (1) F/Y(1 −σ) (2) F/ Y(1 +σ) (3) F(1 − 2σ)/Y(4) F/ Y(1 +2σ)
Answer» Correct option (3) F(1 − 2σ)/Y Explanation: Tensile strain on each face Y/ F Lateral strain due to the other two forces acting on perpendicular faces= −2σF/Y Total increase in length = (1 − 2σ)F/Y

18.

On all the six surfaces of a unit cube, equal tensile force of F is applied. The increase in length of each side will be (Y = Young's modulus, σ = Poisson’s ratio) (1) F/Y(1 −σ) (2) F/ Y(1 +σ) (3) F(1 − 2σ)/Y(4) F/ Y(1 +2σ)

Answer»

Correct option (3) F(1 − 2σ)/Y

Explanation:

Tensile strain on each face Y/ F

Lateral strain due to the other two forces acting on perpendicular faces= −2σF/Y

Total increase in length = (1 − 2σ)F/Y

Discussion

19.	(a) Spring constant is directly proportional to the length of the wire. (b) The spring constant is directly proportional to the cross – sectional area of the wire. (c) The spring constant is inversely proportional to the length of the wire. (d) The spring constant is inversely proportional to the cross sectional area of the wire. (1) b, c (2) a, b (3) a, d (4) c, d
Answer» The Correct option is (1) b, c

Discussion

20.	When a very long rod suspended in air, will break under its own weight. The maximum length of the rod will depend on (a) Breaking stress (b) Density (c) Cross – sectional (d) Acceleration due to gravity (1) a, b, c (2) a, b, d (3) b, c, d (4) a, b, c, d
Answer» The Correct option is (2) a, b, d

Discussion

21.	Match the following. List – I List – II (a) Annealing (e) Increasing the strength of a solid (b) Compressibility (f) Maximum stress for which an object may not break (c) Tensile strength (g) Slow cooling after heating(d) Work hardening (h) Reciprocal of Bulk modulus (1) a – e, b – g, c – f, d – h (2) a – e, b – f, c – g, d – h (3) a – g, b – f, c – h, d – e (4) a – g, b – h, c – f, d – e
Answer» (4) a – g, b – h, c – f, d – e

Discussion

22.	Assertion (A): A wire may be stiffer than another wire B. But B may stronger than A. Reason (R): A high young’s modulus does not necessarily imply a high value for the breaking stress. (1) Both A and R are true, and R is the correct explanation of A (2) Both A and R are true, but R is not the correct explanation of A (3) A is true but R is false (4) R is true but R is false
Answer» (1) Both A and R are true, and R is the correct explanation of A

Discussion

23.	Four springs of force constants K1=1000N/m, K2=1500 N/m, K3=2500 N/m and K4=2000 N/m are subjected to different loads producing same extension. Arrange the springs with work done in descending order(1) 1,2,3,4 (2) 3, 4, 1, 2 (3) 3, 2, 1, 4 (4) 3, 4, 2, 1
Answer» (4) 3, 4, 2, 1.

Discussion

24.	If the interatomic spacing in a steel wire is 3A° and Y steel = 20x10^ 10N/m2 then force constant
Answer» Interatomic space = 3A° = 3 x 10^-10 m Force Constant = Y x Interatomic space (change in length) = 20 x 10¹⁰ x 3 x 10^-10 = 60 N/m

24.

If the interatomic spacing in a steel wire is 3A° and Y steel = 20x10^ 10N/m2 then force constant

Answer»

Interatomic space = 3A° = 3 x 10^-10 m

Force Constant = Y x Interatomic space (change in length)
= 20 x 10¹⁰ x 3 x 10^-10 = 60 N/m

Discussion

25.	Arrange the following materials in the increasing order of elasticity (a) Steel (b) Lead (c) Rubber (d) Glass (1) c, b, d, a (2) a, b, c, d (3) a, d, b, c (4) b, d, a, c
Answer» (1) c, b, d, a.

Discussion

26.	Arrange the compressibility of the liquids Mercury (M) Ethyl alcohol (E). Glycerin (G), and Water (W), in the decreasing order. (1) E, W, G, M (2) M, G, W, E (3) E, G, W, M (4) M, W, G, E
Answer» (1) E, W, G, M

Discussion

27.	Arrange the elastic modulii, stretch modulus (Y), shear modulus (n) and bulk modulus (K), in the decreasing order for typical materials. (1) Y, n, K (2) Y, K, n (3) K, Y, n (4) n, K, Y
Answer» The Correct option is (2) Y, K, n

Discussion

28.	Arrange the following parameters for elasticity, yield point (Y), Limit of proportionality (P), range of Hooke’s law (H) and Breaking stress (B)., in the increasing order of stress. (1) B, Y, P, H (2) H, Y, P, B (3) H, P, Y, B (4) H, Y, B, P
Answer» (3) H, P, Y, B

Discussion

29.	Assertion (A): A hippopotamus has thicker legs for its size than a mouse does. Reason (R): The compressive load on the leg bones of an animal depends on its weight, which in turn varies as the cube L3 of a representative linear dimension L such as its length or height. The strength of a bone, however, depends on its cross –sectional area which for similar animals varies as L2 . A large animal must have relatively thicker leg bones than a small one because L3 increases faster than L2 (1) Both A and R are true, and R is the correct explanation of A (2) Both A and R are true, but R is not the correct explanation of A (3) A is true but R is false (4) R is true but R is false
Answer» (1) Both A and R are true, and R is the correct explanation of A

Discussion

30.	A piece of copper and having internal cavity weighs 264 gm in air and 221 gm when it is completely immersed in water. Find the volume of the cavity. The density of copper is 8.8 gm/cc.
Answer» Mass of copper in air = 264 gm Mass of copper in water = 221 gm Apparent loss of mass in water = 264 – 221 = 43 gm ∴ Mass of water displaced by copper piece when completely immersed in water is equal to 43 gm. Volume of water displaced = (mass of water displaced/density of water) = 43/1.0 = 43.0 cc ∴ Volume of copper piece including volume of cavity = 43.0 cc Volume of copper block only = mass/density = 264/8.8 =30.0 cc Volume of cavity = 43.0 – 30.0 = 13.0 cc.

30.

A piece of copper and having internal cavity weighs 264 gm in air and 221 gm when it is completely immersed in water. Find the volume of the cavity. The density of copper is 8.8 gm/cc.

Answer»

Mass of copper in air = 264 gm

Mass of copper in water = 221 gm

Apparent loss of mass in water = 264 – 221 = 43 gm

∴ Mass of water displaced by copper piece when completely immersed in water is equal to 43 gm.

Volume of water displaced = (mass of water displaced/density of water)

= 43/1.0 = 43.0 cc

∴ Volume of copper piece including volume of cavity = 43.0 cc

Volume of copper block only = mass/density = 264/8.8 =30.0 cc

Volume of cavity = 43.0 – 30.0 = 13.0 cc.

Discussion

31.	Which of the following relations is not correct Y = young's modulus, K = bulk modulus, n= rigidity modulus, σ = poisons ratio (1) 1/Y = 9 η K/(3K +η ) (2) Y/ η = 2(1 +σ ) (3) Y/3 K = (1 -2σ ) (4) (Y/η ) +(Y/3K)=3
Answer» (4) (Y/η ) +(Y/3K)=3

Discussion

Explore topic-wise InterviewSolutions in .

A wire elongates by l mm when a load W is hanged from it. If the wire goes over a pulley and two weights W each are hung at the two ends, the elongation of the wire will be (in mm) (1) zero (2) l/2 (3) l (4) 2l

The property of metals whereby they could be drawn into thin wires beyond their elastic limit without breaking is (1) Ductility (2) Malleability (3) Elasticity (4) Hardness

The possible value of Poisson’s ratio is (1) 0.9 (2) 0.8 (3) 0.4 (4) 1

A heavy mass is attached to a thin wire and is whirled in a vertical circle. The wire is most likely to break (1) When the mass is at the lowest point (2) When mass is at the highest point (3) When wire is horizontal (4) When mass is at an angle of cos-1 (1/√2) from upward vertical

The breaking stress of a wire depends on (1) Material of a wire (2) Shape of cross section (3) Length of the wire (4) Radius of the wire

Steel is preferred for making springs over copper because (1) Young's modulus of steel is more than that of copper ( 2) Steel is cheaper (3) Young's modulus of copper is more ( 4) Steel is less likely to be oxidized

Steel is preferred for making springs over copper because (1) Young's modulus of steel is more than that of copper (2) Steel is cheaper (3) Young's modulus of copper is more (4) Steel is less likely to be oxidized

The following four wires are made of the same material subjected to same force arrange them with their elongations in ascending order(a) l = 50cm and r = 0.5mm (b) l = 100cm and r = 1mm (c) l = 200cm and r = 2mm (d) l = 300cm and r = 3mm (1) a, b, c, d (2) c, d, a, b (3) a, d, c, b (4) d, c, b, a

A body subjected to strain a number of times does not obey Hooke's law due to (1) Yield point (2) Breaking stress (3) Elastic fatigue (4) Permanent set

Match the following. List I List II(a) Spring constant (e) 1/2 (stress)2/Y(b) Tensile strength(f) Δp/ΔV/V(c) Bulk modulus (g) Breaking stress (d) Potential energy/ Unit volume(h) AY/L(1) a-h, b-g, c-f, d-e (2) a-g, b-h, c-e, d-f (3) a-e, b-h, c-f, d-g (4) a-h, b-e ,c-f, d-g

Consider an ideal mono-atomic gas of volume at pressure P. The bulk modulus at constant temperature is (1) p/2 (2) P (3) γ P (4) PdP/dV

Which of the following substances has the highest elasticity? (1) Rubber (2) Steel (3) Copper (4) Wood

The modulus of elasticity is dimensionally equivalent to (1) Stress (2) Surface tension (3) Strain (4) Coefficient of viscosity

The strain produced in the stretched spring is (1) Volume strain (2) Shearing strain (3) Tensile strain (4) None of the above

On all the six surfaces of a unit cube, equal tensile force of F is applied. The increase in length of each side will be (Y = Young's modulus, σ = Poisson’s ratio) (1) F/Y(1 −σ) (2) F/ Y(1 +σ) (3) F(1 − 2σ)/Y(4) F/ Y(1 +2σ)

When a very long rod suspended in air, will break under its own weight. The maximum length of the rod will depend on (a) Breaking stress (b) Density (c) Cross – sectional (d) Acceleration due to gravity (1) a, b, c (2) a, b, d (3) b, c, d (4) a, b, c, d

Four springs of force constants K1=1000N/m, K2=1500 N/m, K3=2500 N/m and K4=2000 N/m are subjected to different loads producing same extension. Arrange the springs with work done in descending order(1) 1,2,3,4 (2) 3, 4, 1, 2 (3) 3, 2, 1, 4 (4) 3, 4, 2, 1

If the interatomic spacing in a steel wire is 3A° and Y steel = 20x10^ 10N/m2 then force constant

Arrange the following materials in the increasing order of elasticity (a) Steel (b) Lead (c) Rubber (d) Glass (1) c, b, d, a (2) a, b, c, d (3) a, d, b, c (4) b, d, a, c

Arrange the compressibility of the liquids Mercury (M) Ethyl alcohol (E). Glycerin (G), and Water (W), in the decreasing order. (1) E, W, G, M (2) M, G, W, E (3) E, G, W, M (4) M, W, G, E

Arrange the elastic modulii, stretch modulus (Y), shear modulus (n) and bulk modulus (K), in the decreasing order for typical materials. (1) Y, n, K (2) Y, K, n (3) K, Y, n (4) n, K, Y

Arrange the following parameters for elasticity, yield point (Y), Limit of proportionality (P), range of Hooke’s law (H) and Breaking stress (B)., in the increasing order of stress. (1) B, Y, P, H (2) H, Y, P, B (3) H, P, Y, B (4) H, Y, B, P

A piece of copper and having internal cavity weighs 264 gm in air and 221 gm when it is completely immersed in water. Find the volume of the cavity. The density of copper is 8.8 gm/cc.

Which of the following relations is not correct Y = young's modulus, K = bulk modulus, n= rigidity modulus, σ = poisons ratio (1) 1/Y = 9 η K/(3K +η ) (2) Y/ η = 2(1 +σ ) (3) Y/3 K = (1 -2σ ) (4) (Y/η ) +(Y/3K)=3