### Young’s Modulus and Breaking Stress:

**Ques:** The Poisson’s ratio cannot have the value

(a) 0.7

(b) 0.2

(c) 0.1

(d) 0.5

Ans. (a)

**Ques:** In the Young’s experiment, If length of wire and radius both are doubled then the value of Y will become

(a) 2 times

(b) 4 times

(c) Remains same

(d) Half

Ans. (c)

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**Ques:** The breaking stress of a wire depends upon

(a) Length of the wire

(b) Radius of the wire

(c) Material of the wire

(d) Shape of the cross section

Ans. (c)

**Ques:** A pan with set of weights is attached with a light spring. When disturbed, the mass-spring system oscillates with a time period of 0.6 s. When some additional weights are added then time period is 0.7*s*. The extension caused by the additional weights is approximately given by

(a) 1.38 *cm*

(b) 3.5 *cm
*(c) 1.75

*cm*

(d) 2.45

*cm*

Ans. (b)

**Ques:** The ratio of the lengths of two wires *A* and *B* of same material is 1 : 2 and the ratio of their diameter is 2 : 1. They are stretched by the same force, then the ratio of increase in length will be

(a) 2 : 1

(b) 1 : 4

(c) 1 : 8

(d) 8 : 1

Ans. (c)

**Ques:** A wire of length 2 *m *is made from 10 cm^{3} of copper. A force *F *is applied so that its length increases by 2 *mm. *Another wire of length 8 *m* is made from the same volume of copper. If the force *F* is applied to it, its length will increase by

(a) 0.8* cm*

(b) 1.6* cm
*(c) 2.4

*cm*

(d) 3.2

*cm*

Ans. (d)

**Ques:** When a uniform wire of radius *r* is stretched by a 2*kg* weight, the increase in its length is 2.00 *mm. *If the radius of the wire is *r*/2 and other conditions remain the same, the increase in its length is

(a) 2.00* mm*

(b) 4.00* mm
*(c) 6.00

*mm*

(d) 8.00

*mm*

Ans. (d)

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**Ques:** Stress to strain ratio is equivalent to

(a) Modulus of elasticity

(b) Poission’s Ratio

(c) Reyhold number

(d) Fund number

Ans. (a)

**Ques:** A load *W* produces an extension of 1*mm* in a thread of radius *r*. Now if the load is made 4*W* and radius is made 2*r* all other things remaining same, the extension will become

(a) 4 *mm*

(b) 16 *mm
*(c) 1

*mm*

(d) 0.25

*mm*

Ans. (c)

**Ques:** The modulus of elasticity is dimensionally equivalent to

(a) Surface tension

(b) Stress

(c) Strain

(d) None of these

Ans. (b)

**Ques:** The extension of a wire by the application of load is 3 *mm*. The extension in a wire of the same material and length but half the radius by the same load is

(a) 12 *mm
*(b) 0.75

*mm*

(c) 15

*mm*

(d) 6

*mm*

Ans. (a)

**Ques:** To keep constant time, watches are fitted with balance wheel made of

(a) Invar

(b) Stainless steel

(c) Tungsten

(d) Platinum

Ans. (a)

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**Ques:** A copper wire and a steel wire of the same diameter and length are connected end to end and a force is applied, which stretches their combined length by 1 cm. The two wires will have

(a) Different stresses and strains

(b) The same stress and strain

(c) The same strain but different stresses

(d) The same stress but different strains

Ans. (d)

**Ques:** Two wires ‘*A*’ and ‘*B*’ of the same material have radii in the ratio 2 : 1 and lengths in the ratio 4 : 1. The ratio of the normal forces required to produce the same change in the lengths of these two wires is

(a) 1 : 1

(b) 2 : 1

(c) 1 : 4

(d) 1 : 2

Ans. (a)

**Ques:** The elastic limit for a gas

(a) Exists

(b) Exists only at absolute zero

(c) Exists for a perfect gas

(d) Does not exist

Ans. (a)

**Ques:** When compared with solids and liquids, the gases have

(a) Minimum volume elasticity

(b) Maximum volume elasticity

(c) Maximum Young’s modulus

(d) Maximum modulus of rigidity

Ans. (a)

**Ques:** The longitudinal strain is only possible in

(a) Gases

(b) Fluids

(c) Solids

(d) Liquids

Ans. (c)

**Ques:** The force constant of a wire does not depend on

(a) Nature of the material

(b) Radius of the wire

(c) Length of the wire

(d) None of the above

Ans. (d)

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**Ques:** Longitudinal stress of 1 km/mm^{2} is applied on a wire. The percentage increase in length is (Y = 10^{11} N/m^{2})

(a) 0.002

(b) 0.001

(c) 0.003

(d) 0.01

Ans. (b)

**Ques:** Why the spring is made up of steel in comparison of copper

(a) Copper is more costly than steel

(b) Copper is more elastic than steel

(c) Steel is more elastic than copper

(d) None of the above

Ans. (c)

**Ques:** Two wires of copper having the length in the ratio 4 : 1 and their radii ratio as 1 : 4 are stretched by the same force. The ratio of longitudinal strain in the two will be

(a) 1 : 16

(b) 16 : 1

(c) 1 : 64

(d) 64 : 1

Ans. (b)

**Ques:** Increase in length of a wire is 1 *mm* when suspended by a weight. If the same weight is suspended on a wire of double its length and double its radius, the increase in length will be

(a) 2 *mm
*(b) 0.5

*mm*

(c) 4

*mm*

(d) 0.25

*mm*

Ans. (b)

**Ques:** When a certain weight is suspended from a long uniform wire, its length increases by one cm. If the same weight is suspended from another wire of the same material and length but having a diameter half of the first one then the increase in length will be

(a) 0.5 *cm
*(b) 2

*cm*

(c) 4

*cm*

(d) 8

*cm*

Ans. (c)

**Ques:** *A* and *B* are two wires. The radius of *A* is twice that of *B*. They are stretched by the some load. Then the stress on *B* is

(a) Equal to that on *A
*(b) Four times that on

*A*

(c) Two times that on

*A*

(d) Half that on

*A*

Ans. (b)

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**Ques:** If the temperature increases, the modulus of elasticity

(a) Decreases

(b) Increases

(c) Remains constant

(d) Becomes zero

Ans. (a)

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