Subtopic: Thermodynamic principles of I.C. engines
Question Statement:
Find the sphericity (Wadell's, surface-area based) of a cylindrical potato sample with diameter 1.0 cm and length 5.0 cm.
Options:
(A) 0.98
(B) 0.70
(C) 0.31
(D) 0.17
Official Answer Key:
B
Step-by-Step Solution & Explanation
Wadell's sphericity = (surface area of a sphere with the same volume as the particle)/(actual surface area of the particle). Volume of cylinder V = πd²L/4 = π(1)²(5)/4 = 3.927 cm³. Equivalent sphere radius re = (3V/4π)^(1/3) = 0.9785 cm; its surface area = 4πre² = 12.04 cm². Actual cylinder surface area = 2π(d/2)² + πdL = 1.571 + 15.708 = 17.28 cm². Sphericity = 12.04/17.28 ≈ 0.70.
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