Wind Tunnel of

DOOOOOOM! 

Tom Dement

Jarad vanSchaik

IB Physics II

Period 3A 


 

 
 
 
 
 

        Table of Contents 

  1. Introduction
  2. Materials Required
  3. Procedures/Set-up
  4. Data Analysis/Data/Graphs
  5. Conclusion/Analysis
  6. Review of Literature, and Bibliography
  7. Return to Research

 

Wind Tunnel of Doooom Final Paper 

      Different objects in our world require different amounts of force to knock them over. Different variables can cause objects to fall either more easily or with more difficulty. For example the weight of an object; two objects with the same size and shape won’t necessarily fall over with the same amount of wind force being applied to them. This is because of weight. For our project we attained a wind tunnel via Mrs. Hubbard and decided we wanted to experiment with the idea of different variables causing a water bottle to get knocked over. We determined the three main factors of an object that would cause them to fall either more easily or with more difficulty were size, shape, and weight.

      We chose size because an object with more surface area facing oncoming wind would fall more easily. We actually tested this because we found that the water bottle we were using as an object only wasn’t falling easily enough. To solve this we cut a flat, square piece of cardboard out and attached it to the water bottle. This added a lot of surface area to the water bottle as well making the shape catch wind more easily.

      We chose shape because we realized from our own personal experience as well as from our research that an object like a spear is going to cut through wind much easier than an object similar to a parachute. By adding a flat piece of cardboard to our object it added very little mass and added a shape that would cause the wind to hit our object more directly as opposed to just sliding off. This cleverly made device allowed for a broader range in our data points so we would be able to see more trends in our data.

      The last factor we chose was weight. This would also be the main variable that we would be testing. We found through our data that an object with more mass will be more difficult to knock over than an object with less mass. This is a fairly simple concept although there are also other factors involved in the weight of an object than just the overall weight. An object with all of its mass at the top of the object is more difficult to knock over than an object with all of its weight at the bottom of the object. However, we decided that it would be too difficult to create a contraption that we could choose where the majority of the mass would be at while still keeping a fairly reliable and accurate experiment. 

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Materials Required:

      -Wind Tunnel -or- some sort of somewhat reliable and measurable machine that blows wind.

      -Ping Pong Ball

      -String

      -Tape

      -Paper

      -Water bottle

      -Water

      -Protractor

      -Scissors

      -Graduated Cylinders

      -Scale

      -Pencil

      -Piece of cardboard 

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Set-Up/Procedures:

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Data/Graphs:

      The mass of our water bottle with the cardboard attached to it had a total mass of 54g.  

      

    Angle of Ping Pong Ball(degrees) Wind Velocity(km/h)
    20 52
    30 41
    40 34
    50 29
    60 24
    70 19
    80 13
    90 0
 Data File1 (Text - tab delimited)

We did some research online and found a website which allowed us to figure out the speed of the wind in our wind tunnel and this is just a graph of that information. The graph looks pretty linear until the final and beginning degrees where it looks exponential. 

Angle of Ping Pong Ball(degrees) Wind Velocity(km/h)
20 52
35 39.69
50 29.79
60 23.2
75 13.31
 
Date File2 (Text - tab delimited)

This is a graph of our ping pong ball angles and the wind velocity that they correlate to.  In order to find the equation to calculate these values we used our calculator to find the Linear Regression for data we found on the Web.  We calculated the linear regression equation to be y= (-.6595238095)(X)+(62.77380952).  We also calculated the Exponential Regression equation to be y= (81.48269014)+(.9786405012)^X.  However we decided to go with the linear regression equation because the graph of the internet showed a strong linear correlation. However, our data for the amount of wind force being applied to the heavier masses showed a slightly more exponential equation. 
 

Angle of Ping Pong Ball(degrees) Amount of Water(ml)
20 300
35 204
50 115
60 101
75 46
 

Data File3 (Text - tab delimited)
 

Wind Velocity(km/h) Amount of Water (mL)
52 300
39.69 204
29.79 115
23.2 101
13.31 46
 
Data File4 (Text - tab delimited)

This graph shows the point of our entire project which was to find out how little wind as possible would cause a bottle to fall over. The one problem with this was that it was harder to control the wind rather than the mass of the bottle so we kind of did this experiment in reverse order to what we would have done had we had a very easy to control wind tunnel. 

Data Analysis:  Basically, this all means that when you put more liquid into a bottle, the more wind velocity is needed to knock the bottle over. This is because when water is added to the bottle; the mass is increased, thus requiring more wind velocity in order to knock the bottle over. This is because the center of gravity is where the average mass of the object is and when you add water to the bottom the mass is greater towards the bottom. This makes the center of gravity lower, and the lower the center of gravity, the more wind velocity is required to knock over the object. 
 
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Conclusion/Analysis:

      In our experiment, we learned more about the scientific process rather than making miraculous discoveries within our specific experiment. We learned about the difficulties of creating a reliable and stable experiment and how hard it is to keep everything the same. We took many precautions to keeping the experiment stables such as leaving the wind tunnel running for extended amounts of time to keep the paper (which was blocking the flow of air) in the exact same place so that the speed wouldn’t vary. As soon as we determined the speed of the wind from the angle of the Ping Pong ball we had to keep everything the same. We had to place the water bottle at the same spot the Ping Pong ball was hanging at so the speed acting on the ball and the bottle would be the same. We could have changed how we dealt with the weight in our experiment slightly by adding more variables to the weight such as where the weight will be located within the water bottle. This would have been very hard to analyze and actually do as well. However we would have like to have evenly dispersed weight throughout the object as we believe that would have made for a more reliable weight. However, with gravity and water as our source of weight this would have been nearly impossible without varying the size of the water bottle.

      Throughout our experiment we felt our data was pretty accurate however we will never really know whether the wind tunnel stayed as consistent as we would have liked. With random gusts here and there and other outside factors causing slight inaccuracies some of our points could be totally off and there really isn’t a great way for us to find out whether they were or not. By leaving the wind tunnel on for so long we’re fairly certain that the speed may have changed once or twice but hopefully not. At 24 km/hr (60 degrees) our point doesn’t really match up with our graphs very well. We’re unsure of what may have caused this but it is probably some sort of human error or possibly the machine just isn’t as consistent as we need.

      We also found that our hands releasing from the water bottle would sometimes cause a jump in the amount of force being applied to the water bottle, causing more inaccuracies at times. We had to be very careful with how we released the bottle from our hands so that it would be standing on its own. We could not place the water bottle inside the tunnel before turning it on because this would cause the paper that was blocking some of the air flow to move. This made the project somewhat difficult but we found if we just had one finger holding it up and letting go quickly we could have as minimal of an effect on the bottle and airflow as necessary. Throughout our data we spent time discussing whether or not our data was linear or exponential. We thought that it must be somewhat exponential at least based on the Ping Pong ball method of measuring the wind speed. Once the ball is parallel with the wind tunnel (a zero degree angle) we really don’t know how fast the ball is traveling. It could be going anywhere from 81.48 degrees (assuming it is in fact an exponential equation) to infinite. The ball has reached its maximum potential by going that speed which is why we avoided measuring it. We tried to stay between 20 degrees and 80 degrees because it’s simply easier to measure and calculate. Most of the data we did find appeared to be somewhat exponential but not very obviously.

      We also decided that the bigger everything is, the easier it would have been to do our experiment. The longer the string attached to the Ping Pong ball the more stables the string would have been. The bigger the protractor is, the easier it is to read the angle. However, because of the size of the wind tunnel we had to make everything smaller and a little more difficult to measure. 

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Bibliography 

Giancoli, Douglas. “Physics”. Prentice Hall, Upper Saddle River, New Jersey. 1998.  

Smith, Tyler. “The Effect of Different Shapes on Aerodynamic Drag” 2003-2004. http://www.selah.k12.wa.us/soar/sciproj2004/TylerS.html 

“The Beaufort Scale” January 1999. http://www.stvincent.ac.uk/Resources/Weather/Charts/beaufort.html 

Merlino, Robert. “Torque and Rotational Motion” July 2004 www.physics.uiowa.edu/~rmerlino/6Fall06/6F06pp_L10.ppt 

Bureau of Meteorology. “Measuring Wind Speed”. 2007. <http://www.bom.gov.au/lam/Students_Teachers/Worksheet16.shtml>

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Review of Literature:

      Because our experiment is fairly unique, it was hard to find sources that relate to our experiment very closely. Our experiment seemed fairly simple when originally choosing it but there are so many factors to account for that it ended up becoming fairly complicated. We used our standard Physics book by Giancoli to help us find what project we wanted to do (as well as the physics website) and our book helped us find formulas to calculate torque, force, velocities, etc. Furthermore, while looking for a sufficient method to measure the speed of the wind in our wind tunnel we used http://www.stvincent.ac.uk/Resources/Weather/Charts/beaufort.html. This site gives a list of wind speeds and how fast we would consider them if they were blowing against us. If nothing else once we can discover the speed of wind this will help us relate to how fast it would be going if we were feeling it full force on our bodies. Then we looked for information on the size and shape of our object and we came across http://www.selah.k12.wa.us/soar/sciproj2004/TylerS.html. This site discusses the differences in the aerodynamics of different objects and gives information on what type of objects resist wind and what types of objects let wind pass it fairly freely. This basically made us decide that we wanted a fairly large and flat object so that the wind won’t need to be super strong to knock the object over (which isn’t a problem because the wind tunnel blows so damn hard). This source didn’t seem to be super official but it seemed like a pretty standard subject that we agreed with before we even found this source. Another fairly valuable source we found was www.physics.uiowa.edu/~rmerlino/6Fall06/6F06pp_L10.ppt which basically spelled out how objects lose their center of gravity and when an object is stable and when it is destined to fall. It’s a power point, it’s simple and easy to read we used this a lot in trying to determine how we would knock over our object and when it would be knocked over and how we could control how it’s knocked over. To calculate wind speed we will be using the method shown on this website http://www.bom.gov.au/lam/Students_Teachers/Worksheet16.shtml. This website uses a string and ping pong ball and allows us to calculate how fast the wind is blowing based on the angle the ping pong ball floats at when holding the string allowing the ball to dangle in the wind. It’s the best way we could find to measure the wind even though this took forever to find. We will have to modify the directions a bit simply because of space but it should at least give us some scale of how we are measuring the wind.

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