The Kool-Aid Maker
Overview
The project that our team did was an overly complex device to make a glass of Kool-Aid. The basic summary of how it works is as follows: First, we launch a small marble through a 6 meter long set of tubing using a stick attached to a slingshot to represent spring energy. When the marble reaches the end of the tubing, a collision happens between the marble and a block that is attached to a soda can lid by a string that we have set up at the end of the tube. From here, two different things happen, first, the block falls off of the platform, and lands on a small basket attached to a ruler. Meanwhile, the block causes tension in the string attached to the soda lid, which causes it to follow along after the block into the cup. When the lid is pulled down, it releases a small container with four pulleys attached to it, which slides down a zip-line that we had constructed. The container then collides with a small L-shaped tower that we have placed near our glass, which has a container attached to it for our Kool-Aid mix, which then tips over and puts the mix into the glass. Meanwhile, the block that fell into the basket on our ruler causes a shift in the center of mass of the ruler, basket, and the battery pack for our drill. This shift in center of mass causes the side of the ruler that the battery pack is resting on to rise, and connects our battery pack to our electric drill. The drill then begins to spin, causing a string connected to another container full of water to begin to pull on the lid we have attached to it. The tension in the string eventually pulls the lid of the container loose, releasing water from the container, into a system of pipes that we installed, and into our glass. Finally, after several overly complex steps, we have a glass of Kool-Aid.
Design Process
Our initial idea was somewhat similar to what we ended up with. The major difference in our designs was that initially we were going to try and rig the drill in such a way that it acted as a stirrer for the finished Kool-Aid product. We eventually scraped this idea and decided to use the drill as a triggering mechanism instead. After we had moved the drill onto our ruler system, we had a different idea for lifting the battery pack into place as well. Instead of using our metal block, we had planned on filling the basket with smaller marbles, enough that adding our large marble to the basket would cause the battery pack to be lifted into position inside the electric drill. After several minutes of testing, however, we found that this method was not very reliable. We then found a metal block lying in the scrap pile, and decided that this amount of weight would be much more reliable to trigger the shift in mass that we needed. After we had finished the steps needed to get the water into the cup, we decided that the device would be better if we had a way to deliver the Kool-Aid mix to the glass as well. We then devised our zip-line idea, and agreed that the soda can lid would be enough to force our cart off of the wall it was resting on after the block yanked out the lid from under the cart. We then came up with the idea for a simple tower that could be tipped over, attached a 20 ounce bottle lid to it with a screw, and set screws into the board to guide the falling tower. All in all, our design changed quite a bit from our original plans, but I believe that it came out much better than we had planned initially.
Above: Our project after our final changes.
Assumptions
We had to make several assumptions in our calculations for this project. We had to get an estimate of our lead weight and the marble we used due to the fact that the tools we used to weigh them did not give accurate measurements. We also assumed that we had no energy loss or friction, due to the fact that we would have multiple unknowns if we included Eloss and we did not know the coefficients of friction for our materials. We also used Google to find our spring constant for our slingshot.
Calculations
Step 1: Spring Energy
1/2kx2 = ½mv2
½(spring constant) (Change in distance)2 = ½ mass of marble * (velocity marble)2
½(200N/m) (.0508m)2 = ½(.0101936 kg) (v2)
.257064 kg*m2/s2 = .050968 kg * v2
v2 = 5.063255376 m2/s2 => 2.250167855 m/s
We used this equation to find the initial speed of our marble after our spring was applied to the marble.
Step 2: Collision
m1v1 + m2v2 = m1v1’ + m2v2’
Mass of marble * initial velo of marble = mass of block * final velo of block
(.0101936 kg)(2.250167855 m/s) = (.30581039 kg) (v2’)
v2’ = .075005009 m/s
This equation shows the final velocity of our metal block after the collision between it and our marble.
Step 3: Center of Mass
Initial Center of Mass for the X direction:
Center of Mass in X = (mass basket * distance from origin in X + mass battery pack * distance from origin in X) / (mass basket + mass battery pack)
X = (m1x1 + m2x2)/ (m1 + m2)
X = ((.0101936799 kg) (1 in) + (.0509683 kg) (9 in))/ (.0101936799 kg + .0509683 kg)
X = 7.6664498 in from origin
Final Center of Mass for X direction:
Center of mass in X = ((mass basket + mass block) * (distance from origin in X)) + (mass battery pack * distance from the origin in X) / (mass basket + mass block + mass battery pack)
X = (m1x1 + m2x2)/ (m1 + m2)
X = ((.0101936799 kg + .30581039 kg) * (1 in) + (.0509683 kg * 9 in))/ ((.0101936799 kg + .30581039 kg) + .0509683 kg)
X = 2.11109 in from origin
These equations show that the Center of Mass for the system on the ruler shifted from an initial position of 7.6664498 inches to 2.11109 inches from the origin, a change in 5.5553598 inches. As our ruler was attached to the board at approximately 4 inches from our origin, this was sufficient enough for our battery pack to be pushed up into the drill.
Above: Diagram of our ruler system, with our final and initial Centers of Mass, along with the point where our ruler is attached to our base.
Materials
Here is a list of our materials that we used and their estimated costs:
1. Drill – $8.50
2. Tubing - $10.05
3. Marbles – $1.50
4. Kool-Aid Packet - $.25
5. Water – Free
6. Ruler - $.25
7. Cartons x 2 - $1.50 total
8. Cup - $.50
9. Funnel - $.39
10. Cup #2 - $2.00
Total: $24.94
Conclusions
Overall I think that our project went fairly well. Our project worked how it was supposed to when we ran it in class, and although it went quickly I think we had a fairly complex set of energy conversions happening in rapid succession. I learned that there are many different ways to solve certain problems or overcome certain obstacles, and you just have to try to think outside the box sometimes to come up with the right solutions. We ran into a couple of problems, most of them minor, but we had several major ones as well. Probably the biggest problem we encountered was when we discovered that our marble did not have enough mass to provide a significant enough change in our center of mass to cause the battery pack to provide power to our drill. After about 10 minutes of brainstorming and scavenging though, we quickly found a suitable replacement and moved on. After that it was mostly minor problems such as discovering our ruler was becoming caught on the stand for our drill, which called for a minor realignment of our ruler system. If I had to do anything differently with the project, I would probably try to find a way to slow it down some. Our project started and ended relatively quickly, and I don’t think most people in the class really noticed that it had done anything by the time it was finished. I would probably try to make it a bit more presentable, as our project didn’t look as well polished as some of the other projects. Overall though, I believe that our project was a success and it was a great feeling of accomplishment when the device worked as planned.
References
The only real reference we had would probably be as we used it for certain things such as the weight of our marbles and to find the spring constant for our slingshot. Other than that our project was original as far as I know, we didn’t really follow anyone else’s model or design to build our project.