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Moving Fluids and Bernoulli's Equation in Physics Lecture

Learn about moving fluids and Bernoulli's equation in this physics lecture. Discover how pressure, speed, and area affect the flow of fluids.

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Moving Fluids and Bernoulli's Equation in Physics Lecture

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  1. Physics 211Lecture 26 Today’s Concepts: A) Moving Fluids B) Bernoulli’s Equation

  2. Clicker Question This picture is A) Real B) Fake

  3. Vacuum gun demo: Atmospheric pressure = big force

  4. Through which hole will the water come out fastest? Clicker Question A B C DP=rgDy

  5. Continuity Equation Flow Rate (volume/time) is the same everywhere a.k.a. Pipe doesn’t leak

  6. Continuity Equation We used the formula A1v1=A2v2, to figure out the speed of the water in the top pipe. It seems we ignored the fact that it was going straight up. Shouldn't gravity have affected it, making it go slower? No – height will change pressurebut not speed… I'm not sure if I'm missing something obvious, but what causes the fluid to go up in the pipe? Difference in pressure (force)

  7. CheckPoint Water flows through a pipe that has a constriction in the middle as shown. How does the speed of the water in the constriction compare to the speed of the water in the rest of the pipe? A) It is bigger B) It is the same C) It is smaller The same amount of water flows through every part of the pipe during an amount of time, so it will flow faster in the constriction

  8. DK = WTOT

  9. Remember Work – Kinetic Energy Eqn Vol Vol

  10. Bernoulli’s Equation a.k.a. Energy Conservation (When height doesn’t change)

  11. CheckPoint Water flows through a pipe that has a constriction in the middle as shown. How does the pressure of the water in the constriction compare to the pressure of the water in the rest of the pipe? A) It is bigger B) It is the same C) It is smaller A) The pressure is higher because there is less area for the water to travel through.. B) It is always the same. C) they're at the same height so P+.5pv^2 must always equal the same thing, and since v is greater in the constriction, pressure must be smaller..

  12. Two empty pop cans are placed about ¼” apart on a frictionless surface. If you blow air between the cans, what happens? A) The cans move toward each other. B) The cans move apart. C) The cans don’t move at all. Clicker Question Blowing air

  13. Bernoulli’s Equation when height changes

  14. CheckPoint hR PR PL hL Bernoulli’sEquation 0 Water flows from left to right along a pipe as shown. The right end of the pipe is twice as high as and also has four times the area of the left end.  Which of the following statements best relates the pressures at the ends of the pipe? A)PL=2PR B) PL=PR C) PL=½ PR D) The relative size of PL and PR depends on the speed of the flow. “Bent pipe was a little confusing.”

  15. Clicker Question Suppose the water isn't moving. The right end of the pipe is twice as high as and also has four times the area of the left end.  Which of the following statements best relates the pressures at the ends of the pipe? A) PL= 2PR B) PL=PR C) PL=½ PR D) PL - PR= rg(hR- hL) hR PR PL hL Bernoulli’sEquation 0

  16. Clicker Question hR PR PL hL Bernoulli’sEquation 0 Water flows from left to right along a pipe as shown. The right end of the pipe is twice as high as and also has four times the area of the left end.  Which of the following statements best relates the pressures at the ends of the pipe? A) PL=2PR B)PL=PR C) PL=½ PR D) PL -PR=rg(hR-hL)+1/2r (vR2-vL2)

  17. Clicker Question hR PR PL hL Bernoulli’sEquation 0 We just saw that PL-PRcan be written in the following way: Is there any reason this has to mean PL= 2PRorPL =PRor PL= ½ PR A) Yes B) No

  18. CheckPoint Water flows from left to right along a pipe as shown. The right end of the pipe is twice as high as and also has four times the area of the left end.  Which of the following statements best relates the pressures at the ends of the pipe? A) PL=2PR B) PL=PR C) PL=½ PR D) The relative size of PL and PR depends on the speed of the flow. hR PR PL hL 0

  19. Flow rate = A*v (units of m3/s)

  20. Volume = Flow rate xtime time = Volume / Flow Rate

  21. same

  22. Please explain the roof problem from the homework. Bernoulli’s Equation Assume the roof is flat.

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