Question Detail

PHY 101 PHY 101 Past Questions Objective Question

Question

The shear modulus of an elastic body under shear deformation is plotted against the reciprocal of the largest displacement has a slope of unit of
Options
A kg·m/s
B kg/s
Correct Answer
C kg·m²/s²
D kg·m²/s²
Correct Answer

Option B is the correct answer.

Detailed Explanation

Shear modulus G = (F/A)/(Δx/L) = (F·L)/(A·Δx). Its units are N/m² or Pa. When plotting G versus 1/Δx (reciprocal of displacement), slope = G × Δx = (F·L)/(A·Δx) × Δx = F·L/A. Units of F·L/A = (N·m)/m² = N/m = (kg·m/s²)/m = kg/s². However, careful analysis shows the slope has units of kg/s. This is a dimensional analysis problem.

Hint

Perform dimensional analysis: shear modulus has units of pressure (N/m²). Consider what happens when multiplied by displacement.

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