Q 11 :

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: Steel is used in the construction of buildings and bridges.

Reason R: Steel is more elastic and its elastic limit is high.

In the light of above statements, choose the most appropriate answer from the options given below               [2023]

• Both A and R are correct but R is NOT the correct explanation of A

   

• Both A and R are correct and R is the correct explanation of A

   

• A is not correct but R is correct

   

• A is correct but R is not correct

   

Q 12 :

For a solid rod, the Young’s modulus of elasticity is $3.2\times {10}^{11}{\text{ Nm}}^{-2}$ and density is $8\times {10}^3{\text{ kg m}}^{-3}$. The velocity of longitudinal wave in the rod will be          [2023]

• $145.75\times {10}^3{\text{ ms}}^{-1}$

   

• $3.65\times {10}^3{\text{ ms}}^{-1}$

   

• $18.96\times {10}^3{\text{ ms}}^{-1}$

   

• $6.32\times {10}^3{\text{ ms}}^{-1}$

   

Q 13 :

Under the same load, wire A having length 5.0 m and cross section $2.5\times {10}^{-5}{\text{ m}}^2$ stretches uniformly by the same amount as another wire B of length 6.0 m and a cross section of $3.0\times {10}^{-5}{\text{ m}}^2$ stretches. The ratio of the Young’s modulus of wire A to that of wire B will be              [2023]

• 1 : 4

   

• 1 : 1

   

• 1 : 10

   

• 1 : 2

   

Q 14 :

The Young’s modulus of a steel wire of length 6 m and cross-sectional area $3{\text{ mm}}^2$ is $2\times {10}^{11}{\text{ N/m}}^2$. The wire is suspended from its support on a given planet. A block of mass 4 kg is attached to the free end of the wire. The acceleration due to gravity on the planet is $\frac{1}{4}$ of its value on the Earth. The elongation of the wire is (Take g on the Earth $=10{\text{ m/s}}^2$)                [2023]

• 1 cm

   

• 1 mm

   

• 0.1 mm

   

• 0.1 cm

   

Q 15 :

Young’s moduli of the material of wires A and B are in the ratio of 1 : 4, while their areas of cross-section are in the ratio of 1 : 3. If the same amount of load is applied to both the wires, the amount of elongation produced in wires A and B will be in the ratio of [Assume length of wires A and B are same]                 [2023]

• 36 : 1

   

• 12 : 1

   

• 1 : 36

   

• 1 : 12

   

Q 16 :

Two wires each of radius 0.2 cm and negligible mass, one made of steel and the other made of brass, are loaded as shown in the figure. The elongation of the steel wire is _______ $\times {10}^{-6}\text{ m}$. [Young’s modulus for steel $=2\times {10}^{11}{\text{ Nm}}^{-2}$ and $g=10{\text{ ms}}^{-2}$]                                [2023]