A 16 mm diameter bar elongates by 0.04% under a tensile force of 16kN...
Given information:
- Diameter of the bar: 16 mm
- Elongation of the bar: 0.04%
- Tensile force applied: 16 kN
- Average decrease in diameter: 0.01%
Calculations:
1. Young's modulus (E) and Shear modulus (G) values are given as options. We need to calculate the Poisson's ratio (V) for each option and compare it with the given value.
2. Poisson's ratio (V) can be calculated using the formula:
V = (E - 2G) / (2E - 2G)
3. For option 1 (E = 210 GPa and G = 77 GPa), substituting the given values in the formula:
V = (210 - 2 * 77) / (2 * 210 - 2 * 77)
V ≈ 0.295
4. For option 2 (E = 199 GPa and V = 0.25), the given value of V can be directly used.
5. For option 3 (E = 199 GPa and V = 0.30), the given value of V can be directly used.
6. For option 4 (E = 199 GPa and G = 80 GPa), substituting the given values in the formula:
V = (199 - 2 * 80) / (2 * 199 - 2 * 80)
V ≈ 0.250
7. Now, we need to calculate the actual value of Poisson's ratio (V_actual) using the elongation and decrease in diameter.
8. The formula for elongation (ε) is given by:
ε = ΔL / L
where ΔL is the change in length and L is the original length.
9. The change in length can be calculated using the tensile force (F) and the cross-sectional area (A) of the bar:
ΔL = F * L / (E * A)
where A = π * (d^2) / 4
10. The decrease in diameter (Δd) can be calculated as:
Δd = d * V_actual
11. Rearranging the above formulas, we get:
V_actual = Δd / d
12. Substituting the given values, we can calculate V_actual for each option.
Results:
- For option 1, V_actual ≈ 0.01 / 16 ≈ 0.000625
- For option 2, V_actual ≈ 0.01 / 16 ≈ 0.000625
- For option 3, V_actual ≈ 0.01 / 16 ≈ 0.000625
- For option 4, V_actual ≈ 0.01 / 16 ≈ 0.000625
Conclusion:
- Comparing the calculated values of V_actual with the given values of V for each option, we can see that options 2 and 4 have the correct values. Thus, the correct options are b) 2 and 4.
A 16 mm diameter bar elongates by 0.04% under a tensile force of 16kN...
Load (P) = 16kN
Diameter (d) = 16mm
% elongation = 0.04%
= 198.94 x 103MPa
= 199 GPa
= 79.6
= 80 GPa
Statement 2 and 4 are correct.