## Mechanical Properties of Solids Questions and Answers Part-6

1. The elastic limit for a gas
a) Exists
b) Exists only at absolute zero
c) Exists for a perfect gas
d) Does not exist

Explanation: Exists

2. If Young's modulus for a material is zero, then the state of material should be
a) Solid
b) Solid but powder
c) Gas
d) None of the above

Explanation: Y is defined for solid only and for powders, Y = 0

3. Liquids have no Poisson's ratio, because
a) It has no definite shape
b) It has greater volume
c) It has lesser density than solid
d) None of the above

Explanation: It has no definite shape

4. A wire of length L and radius r is rigidly fixed at one end. On stretching the other end of the wire with a force F, the increase in its length is l. If another wire of same material but of length 2L and radius 2r is stretched with a force of 2F, the increase in its length will be
a) l
b) 2l
c) $\frac{l}{2}$
d) $\frac{l}{4}$

Explanation:

5. In steel, the Young's modulus and the strain at the breaking point are $2\times10^{11} Nm^{-2}$   and 0.15 respectively. The stress at the breaking point for steel is therefore
a) $1.33\times10^{11} Nm^{-2}$
b) $1.33\times10^{12} Nm^{-2}$
c) $7.5\times10^{-13} Nm^{-2}$
d) $3\times10^{10} Nm^{-2}$

Explanation:

6. Which of the following statements is correct
a) Hooke's law is applicable only within elastic limit
b) The adiabatic and isothermal elastic constants of a gas are equal
c) Young's modulus is dimensionless
d) Stress multiplied by strain is equal to the stored energy

Explanation: In accordance with Hooke’s law

7. The force required to stretch a steel wire of $1 cm^{2}$ cross-section to 1.1 times its length would be $\left(Y=2\times10^{11} N\right)$
a) $2\times10^{6} N$
b) $2\times10^{3} N$
c) $2\times10^{-6} N$
d) $2\times10^{-7} N$

Explanation:

8. Which one of the following substances possesses the highest elasticity
a) Rubber
b) Glass
c) Steel
d) Copper

Explanation: Steel

9.Which one of the following quantities does not have the unit of force per unit area
a) Stress
b) Strain
c) Young's modulus of elasticity
d) Pressure

Explanation: Stress = $\frac{Force}{area}$
Strain = $\frac{Stress}{Y}$