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Discussion Forum



1)

The mass of a hydrogen molecule is 3.32 x10-27 kg. If 1023hydrogen molecules strike per second, a fixed wall of area 2 cm2 at an angle of 45° to the normal and rebound elastically with a speed of 103 m/s, then the pressure on the wall is nearly


A) $2.35\times 10^{3} N/m^{2}$

B) $4.70\times 10^{3} N/m^{2}$

C) $4.70\times 10^{2} N/m^{2}$

D) $2.35\times 10^{2} N/m^{2}$

Answer:

Option A

Explanation:

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Momentum imparted due to first collision

$\Rightarrow 2mv\sin45$ =$\sqrt{2mv}$      \[[\therefore sin45^{0}=\frac{1}{\sqrt{2}}]\]

$\therefore$    Pressure on surface

 = $\frac{n\sqrt{2}mv}{Area}=\frac{10^{23}\times \sqrt{2}\times 3.32\times 10^{-27} \times10^{3}}{(2\times  10^{-2})^{2}}$

$p =2.35\times 10^{3} N/m^{2}$