21. A rod of length L and uniform cross-section area A is rigidly fixed at its top and is hanging. At any section which is at a distance x from the lower end, the stress due to its self-weight is proportional

- 1/x
- x
^{2} - 1/x
^{2} - x

22. A pull of 20 t is suddenly applied to a rod of cross-sectional area 40 cm^{2}. The stress produced in the rod is equal to

- 0.5 t/cm
^{2} - 1.0 t/cm
^{2} - 2.0 t/cm
^{2} - 4 t/cm
^{2}

23. A steel bar is heated from 20°C to 35°C and it is free to expand. Then bar will have

- Tensile stress
- No stress
- Compressive stress
- Shear stress

24. A brass tube has enclosed a steel bar and they have equal cross-sectional area. The Young’s modulus of elasticity is 200 GPa and 100 GPa for steel and brass respectively. Then the ratio of stress developed in the steel bar to that in the brass tube under compression is

- 1
- 0.5
- 2
- 1.5

25. The stress in a steel bar is given as 250 kN/m^{2} and length of the bar is 40m. Calculate the shortening of the bar if E = 2.14 × 10^{5} N/mm^{2}.

- 0.250 mm
- 0.305 mm
- 0.160 mm
- 0.0467 mm

26. A steel bar having cross-sectional area of 100π mm^{2} is subjected to a tensile force of 50 kN. Determine the tensile stress.

- 150 MPa
- 175.25 MPa
- 200.05 MPa
- 159.15 MPa

27. A prismatic bar has a cross-section of 25 mm × 50 mm and a length of 2000 mm. Under an axial load of 100 kN, the measured elongation of the bar is 2 mm. The tensile stress and % strain in the bar are

- 80 MPa and 0.1%
- 0.08 GPa and 1.0%
- 80 N/mm
^{2}and 1% - 800 MPa and 0.01%

28. A bar of copper and bar of steel form a composite system, which is heated to a temperature of 40 °C. The stress in steel bar is

- Tensile
- Compressive
- Zero
- Shear

29. A steel bar of 8 mm is heated from 10°C to 25°C and the bar is free to expand. The bar will induce

- Tensile stress
- No stress
- Compressive stress
- Shear stress

30. The stress in a body, when suddenly loaded is ________ the stress when same load is applied gradually

- equal to
- one half
- twice
- four times