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Venturi meter help

  • Thread starter ahello888a
  • Start date
23
0
Venturi meter help!!!

1. Homework Statement
A venturi meter is measuring the flow of water; it has a main diameter of 3.0 cm tapering down to a throat diameter of 1.0 cm. If the pressure difference is measured to be 16 mmHg, what is the speed of the water entering the venturi throat?


2. Homework Equations

-+P_2+%7D+%5Cright%29%7D%7D%7B%7B%5Crho+%5Cleft%28+%7BA_1%5E2+-+A_2%5E2+%7D+%5Cright%29%7D%7D%7D.gif


Got that equation from a previous part of the problem where it asked me to "Show that the flow speed measured by a venturi meter (see Figure 13–32 in the textbook) is given by the relation"

3. The Attempt at a Solution

I used [tex]\rho[/tex] to be density of water. I converted the diameters to radius in meters. I converted the pressure to "m-Hg". I get 1.77*10^-5. The homework program keeps telling me I'm wrong. I can't see what I'm doing wrong. Thank You for the help!
 

Attachments

tiny-tim

Science Advisor
Homework Helper
25,790
247
Hi ahello888a! :smile:

(you said mmHg as the top, and m Hg at the bottom … is that a typo?)

erm … we need to see your full calculation if we're going to find out where it's wrong! :wink:
 

stewartcs

Science Advisor
2,177
3
Re: Venturi meter help!!!

1. Homework Statement
A venturi meter is measuring the flow of water; it has a main diameter of 3.0 cm tapering down to a throat diameter of 1.0 cm. If the pressure difference is measured to be 16 mmHg, what is the speed of the water entering the venturi throat?


2. Homework Equations

-+P_2+%7D+%5Cright%29%7D%7D%7B%7B%5Crho+%5Cleft%28+%7BA_1%5E2+-+A_2%5E2+%7D+%5Cright%29%7D%7D%7D.gif


Got that equation from a previous part of the problem where it asked me to "Show that the flow speed measured by a venturi meter (see Figure 13–32 in the textbook) is given by the relation"

3. The Attempt at a Solution

I used [tex]\rho[/tex] to be density of water. I converted the diameters to radius in meters. I converted the pressure to "m-Hg". I get 1.77*10^-5. The homework program keeps telling me I'm wrong. I can't see what I'm doing wrong. Thank You for the help!
Start by writing out the energy balance using the Bernoulli equation.

Hints:
Assume the elevation change is zero.
Neglect the small friction.
Use the continuity equation.

Hope this helps.

CS
 

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