When strain is produced in a body within elastic limit, its internal energy:
1. Remains constant                  
2. Decreases
3. Increases                               
4. None of the above

A wire is suspended by one end. At the other end a weight equivalent to 20 N force is applied. If the increase in length is 1.0 mm, the increase in energy of the wire will be

1. 0.01 J                               
2. 0.02 J
3. 0.04 J                               
4. 1.00 J

The ratio of Young's modulus of the material of two wires is 2 : 3. If the same stress is applied on both, then the ratio of elastic energy per unit volume will be-

1. 3 : 2                                   

2. 2 : 3

3. 3 : 4                                   

4. 4 : 3

The stress versus strain graphs for wires of two materials A and B are as shown in the figure. If $Y_A$ and $Y_B$ are the Young ‘s modulii of the materials, then

1. $Y_B=2Y_A$

2. $Y_A=Y_B$

3. $Y_B=3Y_A$

4. $Y_A=3Y_B$

If a spring extends by x on loading, then the energy stored by the spring is (if T is tension in the spring and k is spring constant)

1. $\frac{T^2}{2x}$                                     

2. $\frac{T^2}{2k}$

3. $\frac{2x}{T^2}$                                     

4. $\frac{2T^2}{k}$

A stretched rubber has:

1. increased kinetic energy.

2. increased potential energy.

3. decreased kinetic energy.

4. decreased potential energy.

When load of 5kg is hung on a wire then extension of 3m takes place, then work done will be

1. 75 joule                            

2. 60 joule

3. 50 joule                             

4. 100 joule

If the force constant of a wire is $K$, the work done in increasing the length of the wire by $l$ is:
1. $\frac{Kl}{2}$
2. $Kl$
3. $\frac{Kl^2}{2}$
4. $Kl^2$

A $5~\text{m}$ long wire is fixed to the ceiling. A weight of $10~\text{kg}$ is hung at the lower end and is $1~\text{m}$ above the floor. The wire was elongated by $1~\text{mm}.$ The energy stored in the wire due to stretching is:
1. zero                        
2. $0.05~\text J$ 
3. $100~\text J$                          
4. $500~\text J$

Two wires of the same diameter of the same material having the length $l$ and $2l.$ If the force $F$ is applied on each, the ratio of the work done in the two wires will be:
1. $1 : 2$
2. $1 : 4$
3. $2 : 1$
4. $1 : 1$