1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What causes gas particles to accelerate so that P = F / A

  1. Dec 15, 2012 #1
    Dear Physics Forums,

    Pressure is force / area, and force is mass * acceleration. When you have a gas in a container, it's said to exert a pressure on its container. Therefore, the particles are accelerating toward the container's walls. What's causing these gas particles to accelerate toward the container? Why can't pressure be momentum / area? Momentum, like force, has a tendency to transfer energy as well to a stationary object (the container's walls).

    Thank you for addressing my confusion,

  2. jcsd
  3. Dec 15, 2012 #2
    You are nearly there.

    Force = rate of change of momentum.

    When a gas particle collides with a container wall it is deflected, suffering a change of momentum (vector change).

    This is experienced as a force and a reaction.

    The pressure is the aggregate of many such collisions, taken over area and time.
  4. Dec 19, 2012 #3

    Philip Wood

    User Avatar
    Gold Member

    Studiot has it. Where you were getting confused is in demanding that the molecule must be accelerating towards the wall. [For an ideal gas we ignore any such effect.] The acceleration occurs when the molecule hits the wall and changes its direction, and therefore its velocity.
  5. Dec 19, 2012 #4
    Excellent point.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook