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Section summary

  • Laminar flow is characterized by smooth flow of the fluid in layers that do not mix.
  • Turbulence is characterized by eddies and swirls that mix layers of fluid together.
  • Fluid viscosity η size 12{η} {} is due to friction within a fluid. Representative values are given in [link] . Viscosity has units of ( N/m 2 ) s size 12{ \( "N/m" rSup { size 8{2} } \) s} {} or Pa s size 12{"Pa" cdot s} {} .
  • Flow is proportional to pressure difference and inversely proportional to resistance:
    Q = P 2 P 1 R . size 12{Q= { {P rSub { size 8{2} } - P rSub { size 8{1} } } over {R} } } {}
  • For laminar flow in a tube, Poiseuille’s law for resistance states that
    R = 8 η l πr 4 . size 12{R= { {8ηl} over {πr rSup { size 8{4} } } } } {}
  • Poiseuille’s law for flow in a tube is
    Q = ( P 2 P 1 ) π r 4 8 η l . size 12{Q= { { \( P rSub { size 8{2} } - P rSub { size 8{1} } \) π`r rSup { size 8{4} } } over {8ηl} } } {}
  • The pressure drop caused by flow and resistance is given by
    P 2 P 1 = R Q . size 12{P rSub { size 8{2} } - P rSub { size 8{1} } =R`Q} {}

Conceptual questions

Explain why the viscosity of a liquid decreases with temperature—that is, how might increased temperature reduce the effects of cohesive forces in a liquid? Also explain why the viscosity of a gas increases with temperature—that is, how does increased gas temperature create more collisions between atoms and molecules?

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When paddling a canoe upstream, it is wisest to travel as near to the shore as possible. When canoeing downstream, it may be best to stay near the middle. Explain why.

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Why does flow decrease in your shower when someone flushes the toilet?

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Plumbing usually includes air-filled tubes near water faucets, as shown in [link] . Explain why they are needed and how they work.

The picture shows water gushing out of a water tap. The faucet in the tap is marked. A pipe connected vertically filled with air is shown at an opening on the water pipe before the tap.
The vertical tube near the water tap remains full of air and serves a useful purpose.
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Problems&Exercises

(a) Calculate the retarding force due to the viscosity of the air layer between a cart and a level air track given the following information—air temperature is 20º C size 12{"20" rSup { size 8{ circ } } C} {} , the cart is moving at 0.400 m/s, its surface area is 2 . 50 × 10 −2 m 2 size 12{2 "." "50" times "10" rSup { size 8{2} } `m rSup { size 8{2} } } {} , and the thickness of the air layer is 6.00 × 10 5 m size 12{6 "." "00" times "10" rSup { size 8{ - 5} } `m} {} . (b) What is the ratio of this force to the weight of the 0.300-kg cart?

(a) 3 . 02 × 10 3 N size 12{3 "." "02" times "10" rSup { size 8{ - 3} } " N"} {}

(b) 1 . 03 × 10 3 size 12{1 "." "03" times "10" rSup { size 8{ - 3} } } {}

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What force is needed to pull one microscope slide over another at a speed of 1.00 cm/s, if there is a 0.500-mm-thick layer of 20º C size 12{"20" rSup { size 12{ circ } } C} {} water between them and the contact area is 8.00 cm 2 size 12{8 "." "00"`"cm" rSup { size 8{2} } } {} ?

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A glucose solution being administered with an IV has a flow rate of 4 . 00 cm 3 /min size 12{4 "." "00"`"cm" rSup { size 8{3} } "/min"} {} . What will the new flow rate be if the glucose is replaced by whole blood having the same density but a viscosity 2.50 times that of the glucose? All other factors remain constant.

1 . 60 cm 3 /min size 12{1 "." "60 cm" rSup { size 8{3} } "/min"} {}

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The pressure drop along a length of artery is 100 Pa, the radius is 10 mm, and the flow is laminar. The average speed of the blood is 15 mm/s. (a) What is the net force on the blood in this section of artery? (b) What is the power expended maintaining the flow?

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A small artery has a length of 1 . 1 × 10 3 m size 12{1 "." 1 times "10" rSup { size 8{ - 3} } `m} {} and a radius of 2.5 × 10 5 m size 12{2 "." 5 times "10" rSup { size 8{ - 5} } `m} {} . If the pressure drop across the artery is 1.3 kPa, what is the flow rate through the artery? (Assume that the temperature is 37º C size 12{"37"°C} {} .)

8.7 × 10 11 m 3 /s size 12{8 "." 7 times "10" rSup { size 8{ - "11"} } `m rSup { size 8{3} } "/s"} {}

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Fluid originally flows through a tube at a rate of 100 cm 3 /s size 12{"100"`"cm" rSup { size 8{3} } "/s"} {} . To illustrate the sensitivity of flow rate to various factors, calculate the new flow rate for the following changes with all other factors remaining the same as in the original conditions. (a) Pressure difference increases by a factor of 1.50. (b) A new fluid with 3.00 times greater viscosity is substituted. (c) The tube is replaced by one having 4.00 times the length. (d) Another tube is used with a radius 0.100 times the original. (e) Yet another tube is substituted with a radius 0.100 times the original and half the length, and the pressure difference is increased by a factor of 1.50.

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Questions & Answers

Three charges q_{1}=+3\mu C, q_{2}=+6\mu C and q_{3}=+8\mu C are located at (2,0)m (0,0)m and (0,3) coordinates respectively. Find the magnitude and direction acted upon q_{2} by the two other charges.Draw the correct graphical illustration of the problem above showing the direction of all forces.
Kate Reply
To solve this problem, we need to first find the net force acting on charge q_{2}. The magnitude of the force exerted by q_{1} on q_{2} is given by F=\frac{kq_{1}q_{2}}{r^{2}} where k is the Coulomb constant, q_{1} and q_{2} are the charges of the particles, and r is the distance between them.
Muhammed
What is the direction and net electric force on q_{1}= 5µC located at (0,4)r due to charges q_{2}=7mu located at (0,0)m and q_{3}=3\mu C located at (4,0)m?
Kate Reply
what is the change in momentum of a body?
Eunice Reply
what is a capacitor?
Raymond Reply
Capacitor is a separation of opposite charges using an insulator of very small dimension between them. Capacitor is used for allowing an AC (alternating current) to pass while a DC (direct current) is blocked.
Gautam
A motor travelling at 72km/m on sighting a stop sign applying the breaks such that under constant deaccelerate in the meters of 50 metres what is the magnitude of the accelerate
Maria Reply
please solve
Sharon
8m/s²
Aishat
What is Thermodynamics
Muordit
velocity can be 72 km/h in question. 72 km/h=20 m/s, v^2=2.a.x , 20^2=2.a.50, a=4 m/s^2.
Mehmet
A boat travels due east at a speed of 40meter per seconds across a river flowing due south at 30meter per seconds. what is the resultant speed of the boat
Saheed Reply
50 m/s due south east
Someone
which has a higher temperature, 1cup of boiling water or 1teapot of boiling water which can transfer more heat 1cup of boiling water or 1 teapot of boiling water explain your . answer
Ramon Reply
I believe temperature being an intensive property does not change for any amount of boiling water whereas heat being an extensive property changes with amount/size of the system.
Someone
Scratch that
Someone
temperature for any amount of water to boil at ntp is 100⁰C (it is a state function and and intensive property) and it depends both will give same amount of heat because the surface available for heat transfer is greater in case of the kettle as well as the heat stored in it but if you talk.....
Someone
about the amount of heat stored in the system then in that case since the mass of water in the kettle is greater so more energy is required to raise the temperature b/c more molecules of water are present in the kettle
Someone
definitely of physics
Haryormhidey Reply
how many start and codon
Esrael Reply
what is field
Felix Reply
physics, biology and chemistry this is my Field
ALIYU
field is a region of space under the influence of some physical properties
Collete
what is ogarnic chemistry
WISDOM Reply
determine the slope giving that 3y+ 2x-14=0
WISDOM
Another formula for Acceleration
Belty Reply
a=v/t. a=f/m a
IHUMA
innocent
Adah
pratica A on solution of hydro chloric acid,B is a solution containing 0.5000 mole ofsodium chlorid per dm³,put A in the burret and titrate 20.00 or 25.00cm³ portion of B using melting orange as the indicator. record the deside of your burret tabulate the burret reading and calculate the average volume of acid used?
Nassze Reply
how do lnternal energy measures
Esrael
Two bodies attract each other electrically. Do they both have to be charged? Answer the same question if the bodies repel one another.
JALLAH Reply
No. According to Isac Newtons law. this two bodies maybe you and the wall beside you. Attracting depends on the mass och each body and distance between them.
Dlovan
Are you really asking if two bodies have to be charged to be influenced by Coulombs Law?
Robert
like charges repel while unlike charges atttact
Raymond
What is specific heat capacity
Destiny Reply
Specific heat capacity is a measure of the amount of energy required to raise the temperature of a substance by one degree Celsius (or Kelvin). It is measured in Joules per kilogram per degree Celsius (J/kg°C).
AI-Robot
specific heat capacity is the amount of energy needed to raise the temperature of a substance by one degree Celsius or kelvin
ROKEEB
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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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