Question

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 area $ 2 \, cm^2$ at an angle of $45^{\circ} $ to the normal, and rebound elastically with a speed of $10^3 \, m/s$ , 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. $2.35 \times 10^2 \, N/m^2$
• D. $4.70 \times 10^2 \, N/m^2$

Answer 1

Answer: (A)

$P=\frac{F}{A}=\frac{2 \cdot n m v \,\cos \,\theta}{A}$
$=\frac{2 \times 10^{23} \times 3.32 \times 10^{-27} \times 10^{3}}{\sqrt{2} \times 2 \times 10^{-4}} \,N / m ^{2}$
$=2.35 \times 10^{3} \,N / m ^{2}$