what is pressure?

Answer 1

Preassure is
1.
1. The act of pressing.
2. The condition of being pressed.
2. The application of continuous force by one body on another that it is touching; compression.
3. (Abbr. P) Physics. Force applied uniformly over a surface, measured as force per unit of area.
4. Meteorology. Atmospheric pressure.
5. A compelling or constraining influence, such as a moral force, on the mind or will: pressure to conform; peer-group pressure.
6. Urgent claim or demand: under the pressure of business; doesn't work well under pressure.
7. An oppressive condition of physical, mental, social, or economic distress.
8. A physical sensation produced by compression of a part of the body.
9. Archaic. A mark made by application of force or weight; an impression.

Answer 2

In Physics,

Pressure = Force / Area

The reason why sharp objects can pierce things well is because the Force is applied to a Small Area and hence the pressure is great.

Answer 3

I'm assuming you're talking about a gas.
Gasses are made up of tiny little particles that float around. As they float, they crash into the walls of the vessel they are in. (Don't worry, they don't get hurt.) When they crash into the walls they exert a force upon that wall. Depending on how many particles crash into the wall and how hard they crash determines the overall force the wall feels. As gases are continuous, the larger the wall, the more force can be exerted ('cause there's more room for more stuff to crash.)
Pressure is simply how we define this behaiviour.

Answer 4

Since you're asking this one in the physics category, I'll forgo the other definitions, as others seem to have it down.

Classically (or practically), pressure arises as the tendency for particles with kinetic energy to want to expand. Because there are many particles in a gas/liquid, they tend to bounce and press against themselves as well as anything that tries to contain them.

Pressure is probably most rigidly definited as the transfer of momentum from a particle to a containing wall. Since a transfer of momentum is necessarily involved in a force, then we can characterize the overall transfer of momentum from many particles to many walls as pressure which is just the average force applied to an area.

Answer 5

pressure or blood pressure is force per unit area that is exert on the walls of the arteries caused by the heart which pumps blood at a rate controlled by the pacemaker. High blood pressure is caused by the smallening of the internar artery diameter. generally in physics pressure is just force exerted per unit area.(pressure is proportional to velocity, p=fv)

Answer 6

Process of pressing steadily, the applying of a firm regular weight or force against something or somebody
The pressure of her hand on his was comforting.

(other)
Constant state of worry and urgency: powerful and stressful demands on somebody’s time, attention, and energy, or one of many demands of this sort

(other)
force that pushes or urges: something that affects thoughts and behavior in a powerful way, usually in the form of several outside influences working together persuasively
(other)
physics force per unit area: the force acting on a surface divided by the area over which it acts. Symbol p
(other)
atmospheric pressure: atmospheric pressure
make somebody do something: to apply great persuasion or a strong influence on somebody to force him or her to do something

Answer 7

P{ressure is basically how much force one thing exerts against another. Put another way, it's how much kick a goup of particles have, in terms of energy.

Maybe to put it better, say you have 100 particles. 50 are really low energy and are on the outside, 50 are really high energy and are on the inside.

The low energy particles on the outside are pretty much just sitting there, maybe vibrating a little. The high energy particles are all bouncing around inside. Whenever a high energy particle glances off of a low energy particle it transfer a bit of energy to it and makes it basically move further away.

When you get a whole bunch of high energy particles all doing this (pushing around the lower energy particles) we tend to get a bubble wehre the higher energy particles push apart the lower energy ones. We say they have higher pressure, because they "press" outward on the olwer energy particles by knocking them around transfering energy and velocity to them, and making them move.

Now, all things generally want to be in equilibrium, or "equal", so things with high pressure will tend to push their way into areas of lower pressure. Areas of lower pressure tend not to resist much, and let the higher pressure stuff come in (just because the higher energy things tend to kick them around and MAKE them move).

Now, as these collisions happen, it takes away some of the energy from the more energetic particle, and transfers it to the less energetic particle.

So, what ends up happening is that eventually the kinetic enrgies (or the amount a particular particle is able to "press" or "push" against another) evens out.

So, eventually the presure evens out until everything is the same pressure.

But, it doesn't always work that way. Pressure and density are related.

See, as you get the same amount of stuff at the same temperature (average kinetic motion), but in a larger space, its density (number of particles versus volume) goes down. This means that more dense things can flow between the less dense particles without collisions happening as often. So, the more dense things will tend to sink toward the center of gravity (in our frame of reference that's the center of the earth). But the higher pressure stuff still is pushing material out of the way, since it can't go down as it's bouncing off the higher density stuff below, it tends to go up. This is how we get bubbles.

Basically the internal pressure causes a bubble to form, pushing apart less energetic particles. But some of those particles fall down, through or around the less tightly packed higher "pressure" atoms. In essence the bubble rises as lower density stuff crowds around and down. Eventually the bubble either expends all its energy and collapses, or it reaches an area of equal density/pressure or it reaches the surface and pops (we call this evaporation when water boils).

Hope that all sort of made sense in my usual rambling style...

Answer 8

force per unit area is called pressure

Answer 9

pressure = force per unit square

or:

p = f / a

where, p = pressure, f = force and a = contact area

...

the SI units are Pa [Pascals] or N/m [Nm^-1]

Answer 10

How about this:
It's a measure of how much force is being exerted by particles against another substance. Like gas against a wall, liquid against your body, etc...