A fixed volume of iron is drawn into a wire of length L. The extension x produced in this wire by a constant force F is proportional to

1. $\frac{1}{L^2}$                                             

2. $\frac{1}{L}$

3. $L^2$                                               

4. L

The length of an elastic string is \(a\) metre when the longitudinal tension is \(4\) N and \(b\) metre when the longitudinal tension is \(5\) N. The length of the string in metre when the longitudinal tension is \(9\) N will be:

How much force is required to produce an increase of 0.2% in the length of a brass wire of diameter 0.6 mm ?

(Young’s modulus for brass = $0.9\times {10}^{11}N/m^2$)

1. Nearly 17 N                        

2. Nearly 34 N

3. Nearly 51 N                      

4. Nearly 68 N

A 5 m long aluminium wire $\left(Y=7\times {10}^{10}N/m^2\right)$ of diameter 3 mm supports a 40 kg mass. In order to have the same elongation in a copper wire $\left(Y=12\times {10}^{10}N/m^2\right)$ of the same length under the same weight, the diameter should now be, in mm

1.   1.75                                  

2.   1.5

3.   2.5                                   

4.   5.0

An iron rod of length 2m and cross section area of 50 X ${10}^{-6} m^2$ , is stretched by 0.5 mm, when a mass of 250 kg is hung from its lower end. Young's modulus of the iron rod is-

1. $19.6\times {10}^{10}N/m^2$                         

2. $19.6\times {10}^{15}N/m^2$

3. $19.6\times {10}^{18}N/m^2$                         

4. $19.6\times {10}^{20}N/m^2$

In which case there is maximum extension in the wire, if same force is applied on each wire

1. L = 500 cm, d = 0.05 mm

2. L = 200 cm, d = 0.02 mm

3. L = 300 cm, d = 0.03 mm

4. L = 400 cm, d = 0.01 mm

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 -

1. 12 mm                                 

2. 0.75 mm

3. 15 mm

4. 6 mm

The adiabatic elasticity of a gas is equal to

1. $\gamma \times$density                               

2. $\gamma \times$volume

3. $\gamma \times$pressure                             

4. $\gamma \times$specific heat

The specific heat at constant pressure and at constant volume for an ideal gas are $C_p$ and $C_v$ and its adiabatic and isothermal elasticities are $E_{\varnothing }$ and$E_{\theta }$  respectively. The  ratio of $E_{\varnothing }$ to $E_{\theta }$ is

1. $C_v/C_p$

2. $C_p/C_v$

3. $C_p{C}_v$

4. $1/C_p{C}_v$

The compressibility of water is $4\times {10}^{-5}$ per unit atmospheric pressure. The decrease in volume of 100 cubic centimeter of water under a pressure of 100 atmosphere will be:

1. 0.4 cc         

2. $4\times {10}^{-5}cc$

3. 0.025 cc       

4. 0.004 cc