|How do the particles of a liquid exert pressure on
|Question Date: 2019-03-15|
This question has been already
answered on ScienceLine.
Fluids (a category which includes both
liquids and gases) exert pressure on a container
by the atoms or molecules comprising the fluid
bouncing off of the walls of the container.
To go a bit farther than that answer, and
getting into why
atoms don't move
through each other, the particles "push" on
each other due to quantum effects which
prevent electrons from occupying the same states
Pauli Exclusion Principle ). While there is
electromagnetic repulsion between the particles of
the fluid and of the container when they are at a
certain distance from each other (because of the
repulsion of like charges), this is rather a
secondary effect; if one were to push the
particles together sufficiently, this
electromagnetic repulsion would be overcome and
the quantum effects would take over.
Liquids and gasses are fluids, which means that
their shape is not rigid and the particles are
constantly moving around – a measure of this
motion is the temperature of the fluid. As these
particles are moving, they collide with the inside
walls of the container and bounce off. This
collision causes a force to be exerted on the
wall of the container as the particle changes
direction. The force exerted by the collective
group of particle collisions with the container
walls is responsible for the pressure that the
liquid exerts on the container.
The three states of matter are solid, liquid, and
gas. Solids contain atoms that are fixed
and do not move. Instead, they vibrate in place.
Liquids and gases, however, are made of
atoms that are in constant random motion, flying
around and bouncing off of whatever container they
are in. Temperature makes them move faster, so
gas particles move faster than liquid
particles. Let’s say you have a water
balloon, the pressure of water molecules bouncing
off of the inside of the balloon is what keeps it
from collapsing. When you squeeze and compress the
balloon, you decrease the amount of space the
atoms have to move around, so they bounce off of
the walls harder and can result in higher
pressure, causing the balloon to pop.
The same way that the particles of a solid do,
except that the liquid, being flexible, exerts
pressure on the sides of the container as well as
on the bottom (although non-rigid solid
material, such as a jar full of marbles, will also
exert pressure on the sides). Normal force pushes
the liquid molecules upward and outward, at which
point they push against the walls of the
Liquids are made of really small particles
called molecules. Let's take water for
example. In a glass of water, there are so many
small water molecules that you cannot see them
with your naked eye. You can only perceive this
collection of water molecules as one continuous
stuff. This is similar to looking at a nice
digital photo---but when you zoom in the photo and
look very closely, you should see that the digital
photo is made of many small squares called pixels.
Unlike the pixels of a photo, however, the
molecules of water are always moving around
randomly. Why? It's because they have
so much energy and nothing is locking them up in
place, so they are free to move around. Because
their movements are random, these molecules
collide with the walls of the container. When
the molecules collide with the wall, they exert a
force on the wall. Pressure is the sum of all
these forces per area of the container wall.
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