Question

The mass of a gas molecule is $4\times {10}^{-30}g$. If ${10}^{23}$ molecules strike per second at 4m${}^2$ area with a velocity ${10}^{7}m{s}^{-1}$, the pressure exerted on the surface will be (in pascal)

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

The correct option is B 2

The force will be the impulsive one when the molecules strike and wall and just attain zero velocity.

For each molecule the force will be $2mv$ (2 assumng striking both the walls)

Total force on wall $=2\times 4\times {10}^{-30}\times {10}^{23}\times {10}^7=8$

Pressure $=$ F/area $=8/4=2$ pascals