A solid uniform metal bar of diameter D and length L is hanging vertic...
A solid uniform metal bar of diameter D and length L is hanging vertic...
Explanation:
When a uniform metal bar of diameter D and length L is hanging vertically from its upper end, the weight of the bar causes it to elongate due to self-weight. The elongation of the bar can be calculated using the following formula:
δ = (4MgL)/(πD^2E)
where δ is the elongation, M is the mass of the bar, g is the acceleration due to gravity, E is the Young's modulus of elasticity of the material, and π is the mathematical constant pi.
Proportional to L and inversely proportional to D^2:
From the above formula, we can see that the elongation of the bar is directly proportional to the length L of the bar and inversely proportional to the square of the diameter D. This means that if we double the length of the bar, the elongation will also double, but if we double the diameter of the bar, the elongation will be reduced to one-fourth of its original value.
Independent of D:
However, we cannot say that the elongation is independent of D, as the formula clearly shows the dependence of elongation on D. Therefore, option 'C' and 'D' are incorrect.
Conclusion:
Hence, the correct answer is option 'B', which states that the elongation of the bar is proportional to L and inversely proportional to D^2.