how come pressure is increase when cross sectional area increase?.?

Question

when area is increase ,the volume get increase so pressure should decrease.because velocity increases

Answer 1

its basically how u see the question.
in fluid dynamics, eq of continuity specifies that a*v = constant so with inc in area, velocity decreases,hence pressure increses

while in solids, the case is not the same , pressure = force/area hence assuming force constant with inc in area, pressure must dec

Answer 2

You have it wrong. Someone is trying to fool you.

Firstly pressue is equal to force per unit area as mentioned by many others. Therefore pressure increases as area is reduced, when force remains constant.

Let me illustrate this with a simple example. Take a plastic bottle ( like a coke bottle)and fill it with water. Make a small hole at one vertical side with a needle at about one inch from the bottom and observe the flow of water from the botttle in a jetstream. Now if you enlarge this hole you will notice that the horizontal distance of the jetsream is reduced due to reduced pressure and enlarged area.

To make sure that this not affected by the falling water level you can put a mark on the side wall of the bottle and keep on adding a steady supply of water to maintain the same level or simply keep the bottle full all the time.

This same principle is applicable when you are spraying coloured water during holi with a manual pump ( pitchkari ). If the force is maintained constant its the size of the orifice ( hole ) that determines how far away the jetstream of water will go.

Answer 3

well,this is the most general doubt as it is contradictory to formula of pressure(force per unit area).try to understand this concept.

In case of any fluid flow through any horizontal pipe if cross-sectional area increases then velocity actually decreases due to increse in volume(for same rate of flow) as a result of which pressure tapping devices are tapped to the pipe from below at the point where pressure is to be measured.hence as volume has increased pressure has to decrease at that point.

Answer 4

Pressure is the result of molecular collisions with the surface of something. If there is no movement of the molecules (absolute 0 temperature) there is no pressure. As a stream of fluid passes faster along a surface the collisions become increasingly glancing blows at an angle to the surface and impart less pressure. It's like hitting a ball against a wall at increasingly more shallow angles. That explanation is from a 1950's aerodynamic book that I've misplaced, but I've never heard a better explanation.

Answer 5

Your question is totally wrong.

Actually when c/s area increases preassure decreases along with the velocity.
See, Q = V.A ie., Quantity is equal to Product of Velocity and C/S area, which implies for the constant flow velocity is inversly proportional to Area.
And P=F/A, Pressure is equal to Force per unit area, which means Pressure is inversly pressure to area for constant force. In our case force is constant as flow is constant. F=ma, m is proportional to Flow(Q). so Pressure reduces with increase in area.

So both pressure and velocity decreases with increase in cross sectional area.

Got it.

Answer 6

pressure=force/area
so when area increases pr will decrease.this the principle used in nozzle. one more thing if area increases velocity will decrease according to the continuity equation a1v1=a2v2. so if any increase in area will be compensated by decrease in velocity

Answer 7

we know,
area * velocity =constant(refer equation of continuity)
so when area increases velocity decreases .
also
pressure*velocity =constant
therefore pressure increases

Answer 8

So what is the question.