PhysicsLAB Lab
Flow Rates

Refer to the following information for the next question.

In this lab we are going to experimentally determine cross-sectional area of a hole drilled in a bucket that will be filled with water.
Each group of three-four students will need the following equipment (there are only four buckets):
  • one bucket
  • 5 meter sticks
  • one stop watch
At some point, you need to make the following measurements of your empty bucket:
  • height of the bottom of the hole above the base of the bucket (cm)
  • height of each liter making above the base of the bucket (cm)
  • diameter of the hole (centimeters to at least one, preferably two decimal places)
  • circumference of the bucket at the 2-liter mark (cm)
  • circumference of the bucket at the 8-liter mark (cm)
  • circumference of the bucket at the 14-liter mark (cm)
  • height of outside bench (cm)
When we go outside, you will fill your bucket up to the 14-liter mark. Make sure that the hole remains covered until you are ready to start the experiment. Place it on a level bench - the bucket must NOT be slanted.
When you are ready to start timing, you must immediately also be ready to place the meter sticks on the ground to mark the range of the water as each liter mark is reached. Remember to get the original 14-liter range when the hole is initially uncovered. [If you wish, you may place a litter more than 14 liters in the buckets and start your timers and range measurements when the water level first reaches the 14-liter mark.]
Remember that the water will have a parabolic trajectory and will splash, so you need to quickly ascertain its range when each time is called. After measuring each range, you can then pick up the meter stick to use for another timing mark.
Someone needs to watch the water levels and tell the timer and the range-finder when to record their measurements.
You will run the experiment twice, each time filling the bucket up to the 14-liter mark and then emptying it. Each run will have its own independent timing and range data.
When you are done, the empty buckets, meter sticks, and stop watches will be returned to the cart to be taken back to the room. Each group will then return to the classroom and place your data into the EXCEL spreadsheet 2-FlowRates.xls.
when you open the spreadsheet, do NOT change any programming in the green/purple/blue cells. You are to only add your information to the yellow cells. Remember to save your file as LastnameLastnameLastname_FlowRates.xls You do not need to print your graphs. When your EXCEL file is finished, complete the following conclusions.
What is the title of your group's EXCEL sheet?

Refer to the following information for the next nine questions.

What first principle did you use in your spreadsheet to calculate the Bernoulli velocities?

If the density of the water had been changed, would your Bernoulli velocities have changed? Explain.

If the experiment had taken place in a chamber that had an ambient pressure of 0.85 atmosphere, would your Bernoulli velocities have changed? Explain.

When measuring the range of your water stream, where in the splash zone did you take your measurement?

How does the elevation of your bucket affect the range of the water stream? If you repeated the lab again, would you raise, lower, or keep your elevation the same? Explain. 

Why would the dV/dt column based the water level in the bucket changing 1 liter divided per time interval be less accurate than using the derivative of the graph of true volume vs time? Where you values ever close? Which values had the smaller percent error? Explain. 

Why did the spreadsheet equate the volume flow rates for the water bucket and the water stream?

The apparent areas of your hole based on the Bernoulli velocities and the water stream velocities were not the same. Which was greater? Hypothesize a reason why this might be true.


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Catharine H. Colwell
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