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Give an example of entrainment not mentioned in the text.

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Many entrainment devices have a constriction, called a Venturi, such as shown in [link] . How does this bolster entrainment?

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Figure shows a venturi tube, a cylindrical tube broader at both the ends and narrow in the middle. The narrow part is labeled as venturi constriction. The flow of fluid is shown as horizontal arrows along the length of the tube toward the right. The flow lines are closer in the center and spread apart at both the ends. There is an opening on the top portion of the narrow section for the entrained fluid to enter.
A tube with a narrow segment designed to enhance entrainment is called a Venturi. These are very commonly used in carburetors and aspirators.

Some chimney pipes have a T-shape, with a crosspiece on top that helps draw up gases whenever there is even a slight breeze. Explain how this works in terms of Bernoulli’s principle.

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Is there a limit to the height to which an entrainment device can raise a fluid? Explain your answer.

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Why is it preferable for airplanes to take off into the wind rather than with the wind?

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Roofs are sometimes pushed off vertically during a tropical cyclone, and buildings sometimes explode outward when hit by a tornado. Use Bernoulli’s principle to explain these phenomena.

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Why does a sailboat need a keel?

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It is dangerous to stand close to railroad tracks when a rapidly moving commuter train passes. Explain why atmospheric pressure would push you toward the moving train.

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Water pressure inside a hose nozzle can be less than atmospheric pressure due to the Bernoulli effect. Explain in terms of energy how the water can emerge from the nozzle against the opposing atmospheric pressure.

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A perfume bottle or atomizer sprays a fluid that is in the bottle. ( [link] .) How does the fluid rise up in the vertical tube in the bottle?

A perfume bottle with a spray cap.
Atomizer: perfume bottle with tube to carry perfume up through the bottle. (credit: Antonia Foy, Flickr)

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If you lower the window on a car while moving, an empty plastic bag can sometimes fly out the window. Why does this happen?

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Problems&Exercises

Verify that pressure has units of energy per unit volume.

P = Force Area , ( P ) units = N/m 2 = N m/m 3 = J/m 3 = energy/volume alignl { stack { size 12{P= { {"Force"} over {"Area"} } ,} {} #size 12{ \( P \) rSub { size 8{"units"} } ="N/m" rSup { size 8{2} } =N cdot "m/m" rSup { size 8{3} } ="J/m" rSup { size 8{3} } } {} # ="energy/volume" {}} } {}

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Suppose you have a wind speed gauge like the pitot tube shown in [link] (b). By what factor must wind speed increase to double the value of h size 12{h} {} in the manometer? Is this independent of the moving fluid and the fluid in the manometer?

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If the pressure reading of your pitot tube is 15.0 mm Hg at a speed of 200 km/h, what will it be at 700 km/h at the same altitude?

184 mm Hg

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Calculate the maximum height to which water could be squirted with the hose in [link] example if it: (a) Emerges from the nozzle. (b) Emerges with the nozzle removed, assuming the same flow rate.

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Every few years, winds in Boulder, Colorado, attain sustained speeds of 45.0 m/s (about 100 mi/h) when the jet stream descends during early spring. Approximately what is the force due to the Bernoulli effect on a roof having an area of 220 m 2 size 12{"220"`m rSup { size 8{2} } } {} ? Typical air density in Boulder is 1 . 14 kg/m 3 size 12{1 "." "14"`"kg/m" rSup { size 8{3} } } {} , and the corresponding atmospheric pressure is 8 . 89 × 10 4 N/m 2 size 12{8 "." "89" times "10" rSup { size 8{4} } `"N/m" rSup { size 8{2} } } {} . (Bernoulli’s principle as stated in the text assumes laminar flow. Using the principle here produces only an approximate result, because there is significant turbulence.)

2 . 54 × 10 5 N size 12{2 "." "54" times "10" rSup { size 8{5} } " N"} {}

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(a) Calculate the approximate force on a square meter of sail, given the horizontal velocity of the wind is 6.00 m/s parallel to its front surface and 3.50 m/s along its back surface. Take the density of air to be 1.29 kg /m 3 size 12{1 "." "29"`"kg/m" rSup { size 8{3} } } {} . (The calculation, based on Bernoulli’s principle, is approximate due to the effects of turbulence.) (b) Discuss whether this force is great enough to be effective for propelling a sailboat.

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(a) What is the pressure drop due to the Bernoulli effect as water goes into a 3.00-cm-diameter nozzle from a 9.00-cm-diameter fire hose while carrying a flow of 40.0 L/s? (b) To what maximum height above the nozzle can this water rise? (The actual height will be significantly smaller due to air resistance.)

(a) 1 . 58 × 10 6 N/m 2 size 12{1 "." "58" times "10" rSup { size 8{6} } " N/m" rSup { size 8{2} } } {}

(b) 163 m

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(a) Using Bernoulli’s equation, show that the measured fluid speed v for a pitot tube, like the one in [link] (b), is given by

v = 2 ρ gh ρ 1 / 2 , size 12{v= left ( { {2 { {ρ}} sup { ' }gh} over {ρ} } right ) rSup { size 8{ {1} slash {2} } } } {}

where h size 12{h} {} is the height of the manometer fluid, ρ size 12{ { {ρ}} sup { ' }} {} is the density of the manometer fluid, ρ size 12{ρ} {} is the density of the moving fluid, and g size 12{g} {} is the acceleration due to gravity. (Note that v size 12{v} {} is indeed proportional to the square root of h size 12{h} {} , as stated in the text.) (b) Calculate v size 12{v} {} for moving air if a mercury manometer’s h size 12{h} {} is 0.200 m.

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Questions & Answers

meaning of the term si units
Chali Reply
what what causes electric current
Chali
what what causes electric current
Chali
Charges(electron)
Caleb
Systeme international unitq@1qa@aaq
Caleb
Correct one international system of units.
Caleb
A stone is dropped down a well, if it take 5 seconds to reach the water, how dip is the well
Mollamin Reply
an aircraft at as steady velocity of 70m/so eastwards at a height of 800me drops a package of supplies .a, how long will it take for the package to rich the ground? b, how fast will it be going as it lands?
Ng Reply
what is hypothesis theory law
Tamba
physics is the science of measurement
Jide Reply
What is physics
Victor Reply
what is physics
Obaro
Good question! Physics is the study of the nature world . Does this help?
Yonn
physics is the study of matter in relations to energy.
Enoch
physics is the science of measurements
Jide
physics is a science concern with nature and properties of matter and energy
Ugomma
what is a parallelogram law of motion?
Nancy
describe how you would find the area of an irregular shaped body?
Chali
Definition for physics
Adesola Reply
It deal with matter and relation to energy
Soughie
physics is the Study of matter in relation to energy.
albert
physics is a natural science that study matter its behaviour and relation to energy.
mohammed
physic tells us more about quantities and measurement also
Kelly
life as we know it that can be measured and calculated
Jesus
what is a reference frame
Chukwu Reply
what is anatomy in relation to physics
Mubarak Reply
how does half life exist
Humble Reply
 The amount of time it takes a radioactive isotope to decay into a stable isotope is different for each radioactive isotope, and is characterized by its “half-life”. An isotope's half-life is the amount of time it takes for half the number of atoms of that isotope to decay to another isotope.
Nardine
what is the difference between Mass and weight
Pjustin
mass is constant while weight varies. unit of mass is kg, unit of weight is newton
Faith
how can a coin float in water and what principle governs it
Mercy Reply
in my opinion that work of surface tension but restrictions on coin is that coin do not break surface energy of molecules but some days before scientists prove that's another types of force
Aman
which force hold floating coins together thats my confusion
Aman
how can a coin float in water and what principle governs it
Mercy Reply
why many of the coin floating in water
Aman Reply
what is hook's law
Momoh Reply
provided the elastic limit is not exceeded,the extension produce in an elastic material is equal to the applied force
Mahmud
What is Andromeda
Chinecherem Reply
👡
Mahmud
What are the international agreed system of unit for physical measurements
Aisher Reply
m, kg, s
Faith
kg , m, s
Faith
si
Aman
meter , kilogram , second
Kelly
international system of units is agreed system because more units are not in mks system so si exist with ampere unit
Aman
Practice Key Terms 2

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Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
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