Young's modulus for a steel wire is 2 x 1011 Pa and its elas

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 Multiple Choice QuestionsMultiple Choice Questions

71.

Find the increase in pressure required to decrease the volume of water sample by 0.01%. Bulk modulus of water = 2.1 × 109 Nm-2 .

  • 4.3x 104 N/m2

  • 1.8 × 107 N/m2 

  • 2.1 × 105 N/m2

  • 3.7 × 104 N/m2


72.

The intensity of each of the two slits in Young's double slit experiment is ICalculate the minimum separation between the points on the screen, where intensities are 2I0 and I0 If fringe width is b

  • b5

  • b8

  • b12

  • b4


73.

Assertion:  A rigid body can be elastic.

Reason: If s force is applied on the rigid, its dimensions may change.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


74.

For a constant hydraulic stress P on an object with bulk modulus (B), the fractional change in the volume of object will be

  • PB

  • BP

  • PB

  • BP2


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75.

Young's modulus for a steel wire is 2 x 1011 Pa and its elastic limit is 2.5 x 108 Pa. By how much can a steel wire 3 m long and 2 mm in diameter be stretched before the elastic limit is exceeded?

  • 3.75  mm

  • 7.50 mm

  • 4.75 mm

  • 4.00 mm


A.

3.75  mm

The cross-sectional area of a wire of radius r = l mm= 10-3m is  A = π r2 = 3.14 x 10-6 m2.
The maximum force that can be applied without exceeding the elastic limit is therefore

          F = FAmax × A

          F = (2.5 × 108 N m-2 ) ( 3.14 × 10-6 m2 )

           F = 785 N

When this force is applied, the wire will stretch by

          ΔL = LY FA

                = 3 m 785 N2 × 1011 Nm2 3.14 × 10-6 m2

                 = 3.75 × 10-3 m

            ΔL = 3.75 mm


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76.

Assertion:  Transverse sound wave does not occurs in gases. 

Reason: Gases cannot sustain shearing strain.

  • If both assertion and reason are true and the reason is correct explanation of assertion.

  • If both assertion and reason are true but reason is not correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


77.

Which of the following graph depicts spring constant k versus length l of the spring correctly?


78.

A body of mass 5 kg moving with a speed of 1.5 m/s on a horizontal smooth surface collides with a nearly weightless spring of force constant k = 5 N/m. The maximum compression of the spring would be

  • 0.5 m

  • 0.15 m

  • 1.5 m

  • 0.12 m


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79.

Assertion:  The size and shape of the rigid body remains unaffected under the effect of external forces. 

Reason:  The distance between two particles remains constant in a rigid body.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


80.

If a wire is extended to a new length l, the work done is

  • Y Al l - l'

  • YAl  l - l' 2

  • 12 YAl  l - l' 2

  • 2. YAl  l - l' 2


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