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Fluid Mechanics -Momentum Equation

  • Thread starter cyt91
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Fluid Mechanics --Momentum Equation

Homework Statement


A large weigh tank is to be used in the calibration of a flow metre. Measurements of weights as a function of time are to be made. Water enters the tank vertically from the flow metering system at a speed of 20 ft/s through a 1.5 in. diameter pipe. If the weight of the empty tank is 50 lbf, determine the scale reading at t=10 s.

I found the reading to be 74.8 lbf but the answer is 212.67 lbf.

Any help is appreciated.

The link to my working.

https://skydrive.live.com/?sc=photos&cid=6b041751c72e14ad#cid=6B041751C72E14AD&id=6B041751C72E14AD%21173
 

Answers and Replies

  • #2
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I am unable to decipher your link. Without considering the change in momentum of the water, I get about 203 pounds. If the pipe discharges vertically downward, you'll have to consider momentum change of the water adding to the weight of the vessel.
 
  • #3
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Thanks for the reply.
I have already solved the question. Turned out there's a mistake when I calculated
the weight of water after 10 seconds and I did not include the gc factor. And yes,
momentum of the falling water is already included in the momentum equation.
 

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