Calculating the number of particles colliding with an area per unit time

In summary, the conversation discusses a problem in which the number of molecules colliding with a small portion of a container's wall is related to pressure, average molecular mass, and average velocity. The conversation also mentions the Ideal Gas Law and temperature-KE equivalence as potential starting points for solving the problem. A hint is given to consider the relationship between pressure and the rate of change of momentum of colliding particles.
  • #1
JDStupi
117
2

Homework Statement


Consider a small portion (area=A) of the inside wall of a container full of gas. Show that the number of molecules colliding with this surface in a time interval Δt is PAΔt/(2mvx avg), where P is the pressure, m is the average molecular mass, and vx avg is the average x velocity of those molecules that collide with the wall.

Homework Equations


PV=NkT, 1/2mv2=3/2kT, P=F/A=m(Δv/Δt)

The Attempt at a Solution



The problem here is that I am not entirely sure where to start and would appreciate some hints as to which way to proceed. I have attempted to see relationships between the Ideal Gas Law, temperature-KE equivalence, and the pressure but have yet to succeed. For those who are interested it is Problem 1.22a in Schroeder's Introduction to Thermal Physics.

Thank you very much for any hints and help
 
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  • #3
If you start with the fact that P=F/A and that F = rate of change of momentum of colliding particles you should get an expression for P .
This expression should contain the details of number of collisions per second ,the change in momentum of each particle and the area A.
Hope this gets you started.
 

1. How do you calculate the number of particles colliding with an area per unit time?

The number of particles colliding with an area per unit time can be calculated by using the formula: N = P * A * v * t Where N is the number of particles, P is the density of particles, A is the area, v is the velocity of particles, and t is the time.

2. What is the unit of measurement for the number of particles colliding per unit time?

The unit of measurement for the number of particles colliding per unit time is typically particles per unit area per unit time (particles/area/time).

3. How does temperature affect the number of particles colliding per unit time?

Temperature affects the number of particles colliding per unit time by increasing the kinetic energy of the particles, causing them to move faster and collide more frequently with the area.

4. Can the number of particles colliding per unit time be calculated for gases and liquids?

Yes, the formula for calculating the number of particles colliding per unit time can be applied to both gases and liquids. However, it may be more accurate for gases as their particles are more widely spread out and easier to measure.

5. How is the density of particles determined for the calculation?

The density of particles can be determined by measuring the mass and volume of a sample of particles. The density is then calculated by dividing the mass by the volume.

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