Question 120 of 130

The mass of a hydrogen molecule is $3.32\times {10}^{-27}kg.$ If ${10}^{23}$ hydrogen molecules strike, per second, a fixed wall of the area $2{cm}^{2}$ at an angle of ${45}^{o}$ to the normal, and rebound elastically with a speed of ${10}^{3}m{s}^{-1},$ then the pressure on the wall is nearly:

A$4.70\times {10}^{2}N{m}^{-2}$B$2.35\times {10}^{3}N{m}^{-2}$C$4.70\times {10}^{3}N{m}^{-2}$D$2.35\times {10}^{2}N{m}^{-2}$

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Answer: (B) $2.35\times {10}^{3}N{m}^{-2}$

$F=2mnVcos\theta$$\Rightarrow P=\dfrac{2mnVcos\theta }{A}$

$\Rightarrow P=\dfrac{2\times 3.32\times {10}^{-27}\times {10}^{23}\times {10}^{3}}{\sqrt{2}\times 2\times {10}^{-4}}$

$\Rightarrow P=2.35\times {10}^{3}N{m}^{-2}$