A uniform rod of mass \(10~\text{kg}\) and length \(6~\text m\) is suspended vertically from the ceiling, as shown in the figure. The cross-sectional area of the rod is \(3~\text{mm}^2,\) and its Young’s modulus is \(2\times10^{11}~\text{N/m}^2.\) The extension in the length of the rod is: (take \(g=10~\text{m/s}^2\))
   
1. \(1~\text{mm}\)
2. \(0.5~\text{mm}\)
3. \(0.25~\text{mm}\)
4. \(1.2~\text{mm}\)

Subtopic:  Elasticity |
 53%
Level 3: 35%-60%
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Choose the correct expression that relates Poisson’s ratio \(\sigma,\) bulk modulus \(B,\) and modulus of rigidity \(G.\)
1. \(\mathit{\sigma}{=}\dfrac{{3}{B}{-}{2}{G}}{{2}{G}{+}{6}{B}}\)

2. \(\mathit{\sigma}{=}\dfrac{{6}{B}{+}{2}{G}}{{3}{B}{-}{2}{G}}\)

3. \(\mathit{\sigma}{=}\dfrac{9BG}{{3}{B}{+}{G}}\)

4. \({B}{=}\dfrac{{3}\mathit{\sigma}{-}{3}{G}}{{6}\mathit{\sigma}{+}{2}{G}}\)
Subtopic:  Elasticity |
 59%
Level 3: 35%-60%
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For a perfectly rigid body, the elasticity is:

1. unity 2. zero
3. infinite 4. indeterminate
Subtopic:  Elasticity |
Level 3: 35%-60%
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Elastic forces are:
1. always conservative
2. not always conservative
3. never conservative
4. none of the above
Subtopic:  Hooke's Law |
 51%
Level 3: 35%-60%
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Select the incorrect definition:

1. Deforming Force: A force that changes the configuration of a body.
2. Elasticity: The property of regaining the original configuration.
3. Plastic body: A body that can be easily melted.
4. Elastic limit: The point beyond which a material begins to flow.

Subtopic:  Elasticity |
 54%
Level 3: 35%-60%
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Two equal and opposite forces, each of magnitude \(F,\) are applied along a rod of transverse sectional area \(A.\) The normal stress on a section \(PQ\) inclined at an angle \(\theta\) to the transverse section is given by:
1. \(\dfrac{F}{A} \mathrm{sin \theta}\) 2. \(\dfrac{F}{A} \mathrm{cos \theta}\)
3. \(\dfrac{F}{2A} \mathrm{sin2 \theta}\) 4. \(\dfrac{F}{A} \mathrm{cos^2 \theta}\)
Subtopic:  Stress - Strain |
Level 3: 35%-60%
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One end of uniform wire of length \(L\) and of weight \(W\) is attached rigidly to a point in a roof and a weight \(W_1\) is suspended from the lower end. If \(A\) is area of cross-section of the wire, the stress in the wire at a height \(3L \over 4\) from its lower end is:
1. \(W_1 \over A\)
2. \(\frac{\left(W_1+\frac{W}{4}\right)}{A} \)
3. \(\left(W_1+ {3W \over 4}\right) \over A\)
4. \(W_1 + W \over A\)
Subtopic:  Stress - Strain |
 76%
Level 2: 60%+
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Consider a uniform beam \(\text{AB},\) which is being pulled by a horizontal force \(F\) applied at the end \(\text A,\) so that it is accelerated uniformly. The cross-section of the beam is \(A.\) Let the stress at the ends \(\text A,\text B\) be \(S_\text A,S_\text B\) and that at the centre \(\text C\) be \(S_\text C.\) Then:
1. \(S_\text A=\text{zero},S_\text B=\text{maximum,}\) \(S_\text C=\text{intermediate}\)
2. \(S_\text A=\text{maximum, }S_\text B=0,\) \(S_\text C=\text{intermediate}\)
3. \(S_\text A=S_\text B=\text{maximum},\) \(S_\text C=\text{zero}\)
4. \(S_\text A=S_\text B=S_\text C=\text{constant throughout}\)
Subtopic:  Stress - Strain |
Level 3: 35%-60%
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An ideal gas has an isothermal bulk modulus of \(B_1.\) Its volume is doubled, isothermally. The bulk modulus is now: 
1. \(B_1\) 2. \(2B_1\)
3. \( \dfrac {B_1}{2}\) 4. \(​​\dfrac {B_1}{\sqrt 2}\)
Subtopic:  Shear and bulk modulus |
Level 3: 35%-60%
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A uniform rod \(AB\) is rotated at a constant angular speed about its end \(A,\) the rotation axis being perpendicular to \(AB.\) During rotation, stresses are set up in the rod. Let the stress at \(A\) be \(\sigma_A\) and that at the centre \(C\) be \(\sigma_C.\) Then:
                   

1. \(\sigma_A=\sigma_C\)
2. \(\sigma_A=2\sigma_C\)
3. \(\sigma_C=2\sigma_A\)
4. \(\sigma_C=\dfrac34\sigma_A\)
Subtopic:  Stress - Strain |
Level 4: Below 35%
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