• # question_answer 2000 cc. of air takes $1{\scriptstyle{}^{1}/{}_{2}}$  minutes to pass through a standard Specimen of sand (5.08 cm high and 5.08 cm in dia.). The manometer indicates pressure as $5\,\text{g/c}{{\text{m}}^{\text{2}}}\text{.}$ In this case the permeability number is: A) 30                                B) 42C) 51                                D) 67

Correct Answer: D

Solution :

Permeability number, $P=\frac{Vh}{pAt}$ $V\text{ }=\text{ }2000\text{ }c.c.,t=1.5\text{ }min,\text{ }h\text{ }=\text{ }5.08\text{ }cm,$ $d\text{ }=\text{ }5.08\text{ }cm,$$p=5\,\text{g/c}{{\text{m}}^{\text{2}}}$ $P=\frac{2000\times 5.08}{5\times \frac{\pi }{4}{{(5.08)}^{2}}\times 1.5}=66.83=67$

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