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Conceptual questions

You can squirt water from a garden hose a considerably greater distance by partially covering the opening with your thumb. Explain how this works.

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Water is shot nearly vertically upward in a decorative fountain and the stream is observed to broaden as it rises. Conversely, a stream of water falling straight down from a faucet narrows. Explain why.

The mass of water that enters a cross-sectional area must equal the amount that leaves. From the continuity equation, we know that the density times the area times the velocity must remain constant. Since the density of the water does not change, the velocity times the cross-sectional area entering a region must equal the cross-sectional area times the velocity leaving the region. Since the velocity of the fountain stream decreases as it rises due to gravity, the area must increase. Since the velocity of the faucet stream speeds up as it falls, the area must decrease.

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Look back to [link] . Answer the following two questions. Why is p o less than atmospheric? Why is p o greater than p i ?

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A tube with a narrow segment designed to enhance entrainment is called a Venturi , such as shown below. Venturis are very commonly used in carburetors and aspirators. How does this structure bolster entrainment?

Figure is a drawing of a tube with a narrow segment labeled as a venture construction. Additional small connection is made at the constriction and allows entrained fluid to enter fluid flow.

When the tube narrows, the fluid is forced to speed up, thanks to the continuity equation and the work done on the fluid. Where the tube is narrow, the pressure decreases. This means that the entrained fluid will be pushed into the narrow area.

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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.

The work done by pressure can be used to increase the kinetic energy and to gain potential energy. As the height becomes larger, there is less energy left to give to kinetic energy. Eventually, there will be a maximum height that cannot be overcome.

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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.

Because of the speed of the air outside the building, the pressure outside the house decreases. The greater pressure inside the building can essentially blow off the roof or cause the building to explode.

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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.

The air inside the hose has kinetic energy due to its motion. The kinetic energy can be used to do work against the pressure difference.

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Questions & Answers

y oxygen is shift to first place
Radhika Reply
What is coriolis firce
Shakeel Reply
Angular accelaration force,as the result of the rotatation of earth
Arzoodan
Due to the rotation of the earth the winds at the equator get deflected in opposite direction and therefore cause some currents in the Northern and Southern hemisphere which are opposite in there spin.
Varsha
Thats correct.
Arzoodan
if cos = x/y then sec = y/x if sin = y/x then cosec = x/y
Jan Reply
if cosβ=x/y then what is cosecβ
Abubakar Reply
. if cosβ=x/y what is cosecβ
Abubakar
if cosΦ=x/y what is cosecΦ
Abubakar
What are the unknown symbols?
Jan
β
Jan
Φ
Jan
It is defined that cosec = 1/sin and sec = 1/cos
Jan
Do you understand this?
Jan
of cours
Arzoodan
∇(f/g) = (g∇f − f∇g)/g^2 , at points x where g(x) 6= 0 please help me to solve the problem ....
11 Reply
sir please add answer sheet of spigel vector analysis ..
11 Reply
In a pulley system 2 boxes r hanging in both sides of pulley. An other box was joined to the left box through a rope & get accelerated downward. If all the boxes have same mass ,then what will be the acceleration of that system ?
bibek Reply
it may be mg
Amalesh
∇(f/g) = (g∇f − f∇g)/g2 , at points x where g(x) 6= 0 plus solve it
11
What is momentum
Rika Reply
is the product of mass to it's velocity (mv)
Ahmed
momentum
oladipupo
quatity of motion present in a body or product of mass and velocity
Shakeel
what is hydration energy
osobase Reply
the energy................................................
Rika
what is momentum
Ogwu Reply
dont know want to know the answer
Rika
it's the product of mass multiplied by velocity
harsha
the quantity of motion possessed by a body is called its momentum.by virtue of which a body can exert a force in the agency which tend to stop it .it is a common experience that stronger force is required to stop more massive body.also faster the body moves harder it is to stop it .this is why
Manoj
momentum is product of mass and velocity and it is denoted by "P".
Manoj
show that the cross product of vector axb=-bxa
Teklu Reply
Nature of the physical low
Rashika Reply
1/2 mv2 =mgh prove that
Rashika
study work energy theorem properly
Rohan
v2=u2+2gh...u=0...so 1/2 mv2=1/2m(2gh)=mgh
Talha
how can I become confident in physics
arshdeep Reply
practice more and more question ,,,,if u get trouble in any one question infact do that again and again.
jyotirmayee
is theory important or numericals
arshdeep
both ,,,,because without understanding theory ,,,,u can't able to solve problemsss or numericals
jyotirmayee
which books I can follow for IIT jee prep for mcq and which for mcq
arshdeep
what can make me good in physics
lovet
how can I solve qsns in physics cuz I understand most of the theories but facing problem during solving the qsns.
Rohan
what can make me good in physics
Rika
Can someone please tell what really happened to planet Pluto
Ejiba Reply
Pluto was consider as a dwarf planet and not a planet a planet should satisfy the three criteria viz.it should have a orbit around the sun,it should be spherical in shap,and it should clear its orbit . since,Pluto satisfy the first two criteria so it was not considered as a planet .
Manoj
but it was seen that earth also not cleared its orbit but earth is a planet so another criteria was made that a planet should have grater gravitational force other than its orbit and earth follow this but Pluto wasn't satisfied this criteria .so Pluto wasn't consider as a planet.since it follow the
Manoj
first two criteria so it gets a another name called dwarf planet
Manoj
what are the first 20 elements in periodic table.
Ejiba Reply
what happened to the rest now, or have you forgotten?
Ejiba
Hydrozen helium lithium berrilium boron carbon nitrogen oxygen flourine neon sodium magnesium aluminium silicon phosphorous sulphur chlorine argon potassium calcium
Rika
you said 20 elements and thats here
Rika
correct
osobase
yes i know
Rika
excuse me any one here
Rika
yes
harsha
what is momentum
Rika
it is the product of mass and velocity
harsha
thanks
Rika
momentum p = mass X velocity
harsha
Hydration energy?
osobase
p= m*v
harsha
Hydration enery?
Rika
Hydration energy?
Rika
The heat energy released when new bonds are made between the ions and water molecules is known as the hydration enthalpy of the ion
harsha
hydration energy is also called as hydration enthalpy.
harsha
yes what is hydration Energy?
osobase
correct
osobase
Tripple point of water?
osobase
yes it is.
harsha
where water exists in all the three states
harsha
at that point it exists as water (liquid) , ice (solid) and vapours (gas)
harsha
yeap
Rika
What is d tripple point pressure of water?
osobase
it's 6 milli bar
harsha
in mmhg?
osobase
mmHg?
osobase
I can't remember the exact number
harsha
76 cm of Hg = 1 bar
harsha
calculate it for 6millibar
harsha
wrong
osobase
okay.
harsha
4.6mmHg
osobase
what is hydrodynamics
Manoj
the branch of physics that deal with the motion of fluids and the force acting on a solid body immersed in it . fluids means a substance that has no fixed shape and yields easily to external pressure viz.gas or liquid in other words a substance that able to flow easily.
Manoj
Practice Key Terms 2

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Source:  OpenStax, University physics volume 1. OpenStax CNX. Sep 19, 2016 Download for free at http://cnx.org/content/col12031/1.5
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