Mechanical Properties of Solids Questions and Answers Part-2

1. The material which practically does not show elastic after effect is
a) Copper
b) Rubber
c) Steel
d) Quartz

Answer: d
Explanation: Quartz

2. If the temperature increases, the modulus of elasticity
a) Decreases
b) Increases
c) Remains constant
d) Becomes zero

Answer: a
Explanation: Because due to increase in temperature intermolecular forces decreases.

3. A force F is needed to break a copper wire having radius R. The force needed to break a copper wire of radius 2R will be
a) F/2
b) 2F
c) 4F
d) F/4

Answer: c

4. The relationship between Young's modulus Y, Bulk modulus K and modulus of rigidity \[\eta\] is
a) \[Y=\frac{9\eta K}{\eta+3 K}\]
b) \[Y=\frac{9Y K}{Y+ 3K}\]
c) \[Y=\frac{9\eta K}{3+ K}\]
d) \[Y=\frac{3\eta K}{9\eta+ K}\]

Answer: a

5. The diameter of a brass rod is 4 mm and Young's modulus of brass is \[9\times10^{10}N\diagup m^{2}\]  . The force required to stretch by 0.1% of its length is
a) \[360\pi N\]
b) 36 N
c) \[144\pi \times10^{3} N\]
d) \[36\pi \times10^{5} N\]

Answer: a

6.If x longitudinal strain is produced in a wire of Young's modulus y, then energy stored in the material of the wire per unit volume is
a) \[yx^{2} \]
b) \[2yx^{2} \]
c) \[\frac{1}{2}y^{2}x \]
d) \[\frac{1}{2}yx^{2} \]

Answer: d

7. In a wire of length L, the increase in its length is l. If the length is reduced to half, the increase in its length will be
a) l
b) 2l
c) \[\frac{l}{2}\]
d) None of the above

Answer: c

8. The Young's modulus of a rubber string 8 cm long and density \[1.5 kg\diagup m^{3} \]   is \[5\times10^{8} N\diagup m^{2} \]  , is suspended on the ceiling in a room. The increase in length due to its own weight will be
a) \[9.6\times10^{-5} m\]
b) \[9.6\times10^{-11} m\]
c) \[9.6\times10^{-3} m\]
d) 9.6 m

Answer: b

9. 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

Answer: b

10. If the length of a wire is reduced to half, then it can hold the ......... load
a) Half
b) Same
c) Double
d) One fourth

Answer: b
Explanation: Breaking force \[\propto\] Area of cross section of wire i.e. load hold by the wire does not depend upon the length of the wire.