A wire has a length \(l_1\) when it is under tension \(T_1,\) and length \(l_2\) when it is under tension \(T_2.\) When it is under a tension \(T_1 + T_2,\) its length is:
1. \(l_1+l_2\)
2. \(\dfrac{l_1T_1+l_2T_2}{T_1+T_2}\)
3. \(\dfrac{l_1T_1-l_2T_2}{T_1-T_2}\)
4. \(\dfrac{l_1T_2+l_2T_1}{T_1+T_2}\)
A wire of cross-section \(A_{1}\) and length \(l_1\) breaks when it is under tension \(T_{1};\) a second wire made of the same material but of cross-section \(A_{2}\) and length \(l_2\) breaks under tension \(T_{2}.\) A third wire of the same material having cross-section \(A,\) length \(l\) breaks under tension \(\dfrac{T_1+T_2}{2}.\) Then:
1. | \(A=\dfrac{A_1+A_2}{2},~l=\dfrac{l_1+l_2}{2}\) |
2. | \(l=\dfrac{l_1+l_2}{2}\) |
3. | \(A=\dfrac{A_1+A_2}{2}\) |
4. | \(A=\dfrac{A_1T_1+A_2T_2}{2(T_1+T_2)},~l=\dfrac{l_1T_1+l_2T_2}{2(T_1+T_2)}\) |
Two wires of identical dimensions but of different materials having Young's moduli \(Y_1, Y_2\) are joined end to end. When the first wire is under a tension \(T,\) it elongates by \(x_1\) while the second wire elongates by \(x_2\) under the same tension \(T.\) The elongation of the composite wire when it is under tension \(T\) is:
1. | \(x_1+x_2\) | 2. | \(\dfrac{Y_1x_1+Y_2x_2}{Y_1+Y_2}\) |
3. | \(\dfrac{x_1+x_2}{2}\) | 4. | \(\dfrac{Y_1x_2+Y_2x_1}{Y_1+Y_2}\) |
1. | tensile, \(\dfrac{F}{3A}\) |
2. | compressive, \(\dfrac{F}{3A}\) |
3. | tensile, \(\dfrac{2F}{3A}\) |
4. | compressive, \(\dfrac{2F}{3A}\) |
1. | \(\dfrac{3 M g l}{A Y}\) | 2. | \(\dfrac{2 M g l}{A Y}\) |
3. | \(\dfrac{3 M g l}{2 A Y}\) | 4. | \(\dfrac{M g l}{A Y}\) |
1. | no stress. | 2. | compressive stress. |
3. | tensile stress. | 4. | shear stress. |
1. | 2. | ||
3. | 4. |
1. | \(B_1\) | 2. | \(2B_1\) |
3. | \( \dfrac {B_1}{2}\) | 4. | \(\dfrac {B_1}{\sqrt 2}\) |