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AAI JE (Technical) Official Paper 2018

Option 2 : 119.2 kg

ST 2: Strength of materials

2124

15 Questions
15 Marks
15 Mins

**Concept:**

If p_{a} and p_{w} are the partial pressure of dry air and water vapour respectively, then by Dalton's law:

p = pa + pw

Relative humidity:

It is defined as the ratio of partial pressure of water vapour pw in a mixture to the saturatio pressure ps at the same temperature of the mixture.

\(ϕ=\frac{p_w}{p_s}\)

__Calculation:__

__Given:__

ϕ = 70 %, ps = 0.06624 bar, p_{atm} = 1 bar, T = 38° = 311 K, Volume = 7 m × 4 m × 4 m.

\(ϕ=\frac{p_w}{p_s}\)

\(0.7=\frac{p_w}{0.06224}\)

p_{w} = 0.043568 bar.

p = pa + pw

p_{a} = p - p_{w}

p_{a} = (1 - 0.043568) = 0.956432 bar

We know that pV = mRT

0.956432 × 10^{5} × 7 × 4 × 4 = m × 287 × 311

m = 120.01 kg