1
$\begingroup$

I am informed that the pressure is due to the collision of particles on the surface.If so on the surface of water in a glass, the air particles could collide to water surface in many different directions and not just normal to the surface.So how can we say pressure if Force normal to surface divided by area?.Even if it is a definintion of force.What is the parallel(horizontal component) doing to the water surface (definitely not moving water in hydrostatics).

  Am I missing something here?.
Improve this question
$\endgroup$
2
  • $\begingroup$ Because the horizontal components (of the particles' motion) are equal and opposite, summing to zero, whereas the vertical components are all in the same direction? $\endgroup$
    – Weather Vane
    Jul 2, 2021 at 12:51
  • $\begingroup$ Your both points are correct. 1) collision part 2) Pressure definition. But I think you are not properly imagining it. Consider a Boat in water and think about the surface in contact of the boat and water $\endgroup$
    – Garvit
    Jul 2, 2021 at 13:00

1 Answer 1

Reset to default
1
$\begingroup$

Weather Vane is basically correct. The atoms or molecules of a fluid are bouncing around at random. Assuming the surface being impacted is rough enough at the sub-microscopic to receive forces components which parallel to the surface, then these forces would be randomly distributed in magnitude and direction. The resultant force can only be normal to the surface.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.