Why does higher velocity creates lower pressure?

Question

Today i learned about pressure.. when the question which part of the spray has a lower pressure we answer inner and we gt wrong!! so our teacher say when a higher velocity creates a lower pressures.. so we asked our teacher why?? she studered with no answer.. could anyone of u out there help me on this question??

Clear Explanation will solve the problem better ^^

Answer 1

I'll try to answer your question based on my basic knowledge on pressure.

The inner part of the spray can has a higher pressure. Because particles move from a region of high pressure to low pressure to achieve a state of equilibrium ( just like diffusion ).

I'm very dubious on this but..

A high velocity creates a region of low pressure because the particles are further apart ( less dense ). Bernoulli's principle states that velocity is inversely proportional to pressure. So high velocity - low pressure and low velocity - high pressure.

I'm sorry if this is wrong and I hope someone can correct me.

Answer 2

Good question, and tough to answer, as you can see from your responses.

A fluid (liquid, or gas) is composed of atoms/molecules ('particles'). I'll refer to a liquid here.....when sitting idle the 'particles' in a liquid (like in a glass of water) are free to move about essentially in equilibrium in all directions macroscopically speaking (large-scale --- you-and-I-scale). This accounts for equal pressure being exerted in all directions in the liquid (fluid). The motion of the particles is what gives rise to pressure, and pressure is just a force acting per unit of area.

This concept is standard in thermodynamics and usually in reference to an average kinetic energy of the particles as a whole, the value of which is not important here. But this energy is when a particle hits the container wall and imparts some of this energy to the container....it's individual contribution of pressure of the liquid as a whole.......make sense??? Add up all these individual 'hits' to the container for the whole fluid and voila`...you have what we perceive as pressure.

If you now take this liquid and send it traveling in one (predominant) direction, you cause all the motion ((predominantly) to be in this one direction. Therefore you necessarily reduce the pressure exerted in the other directions.

Friction in the liquid is not the same throughout the volume of the liquid. It varies because of friction with the sides of the transport media (tubing, hose, pipe, creek bed, river bed, etc), and also due to friction with its self.

This low pressure causes certain effects in the liquid and in neighboring fluids (liquids or gases). For example....water in your shower causes the shower curtain to draw up toward you...which is a royal pain. The lower pressure created by each stream adds and creates an overall effect of lower pressure of the shower spray as a whole. The reason this happens is because the speed of each stream causes the air in the vicinity of each stream to also speed up in the direction of the water, thus lowering the pressure in this region, causing the higher pressure air adjacent to it to rush inward to take the place of the lower pressure air being carried along by the water. This then becomes a cycle which gives the overall effect of what you see in the shower of the curtain being drawn inward to you.

This is where the high/low pressure stuff comes from and it's actually easy to see how this happens, but the key is knowing the liquid (fluid) is made of particles and that their movement in the fluid is what gives rise to the pressure. Making the fluids move...causing these particles to move, necessarily has to influence the pressure, as I described.

Hope this makes sense.

:)

Answer 3

It does not "create" higher pressure as such

Instead, look at it from law of conservation of energy

Energy due to pressure gets converted into energy due to velocity (kinetic energy)

So higher the velocity the lower the pressure

In an eductor (nozzle device) due to the sharp reduction in area of cross section, the velocity increase sharply in order to maintain the same flow rate per unit or area

The pressure in the region drops so much that it falls below atmospheric pressure

Eductors are used to create "suction" effect and can be used to pump out fluids very effectively

Ever notice how the shower curtains start blowing out at the bottom edges when you take a shower?

Its because the jets of water (high velocity = low pressure) from the shower head are sucking in air and causing a small "wind" to blow downwards from the shower head and out from the bottom edge of the curtain

Answer 4

Yes, this is confusing. Try thinking of it the 'other way' around. There is a reason why the velocity is increased. What could it be? The only solution is that there must be a drop in pressure; that is, the fluid is moving from a higher pressure to a lower pressure, and that difference in pressures fuels the increase in speed. So it is a matter of the conservation of energy. If the speed increased and the pressure did not decrease, there would be an imbalance in the energetics of the fluid: energy would be appearing out of nowhere, and - oops - apart from StarTrek and the big bang and sometimes quantum mechanics, we do not encounter that, and certainly not in science exams!

Oh. You are new to Yahoo Answers. May I suggest that you get into the habit of taking the trouble to pick a 'best answer'?  I do not mean to select this one - any one if fine. It is a way that the people who give answers can feel that their efforts are valued in some way. You could think of it as a way of saying thanks. Iif  it goes to a public vote, any silly answer can be selected.