The Obstacle Course

Transcription

1 The Obstacle Course Myles Smith, Troy Holcomb, and Chris Wheeler Team 8 Section: B2

2 2 Abstract We were asked to create a Rube Goldberg device, which explored and demonstrated different topics of physics we learned throughout the semester. Our design consists of a series of different steps that begins with a hot wheels car racing down a track and ends with a lego man doing a flip. We explore the conservation on energy is every step of our project, and use rotational motion to raise a UT flag. The flag is raised by creating potential energy by winding up a dowel with a rubber band on it. The propeller on the dowel is stopped by a balloon, but when the balloon is popped the propeller and the dowel spin to wind up the string and raise the flag.

3 3 The objective of this project was to design and build a Rube Goldberg device, which is an inefficient and complicated device to do something simple. Our device had to display a UT banner, perform independently, and start and be started by another team s device. In the creation of the Rube Goldberg device, we also had to demonstrate some of the knowledge that we had learned throughout the semester in EF 151. We started our project by figuring out how we wanted to raise the flag. It was difficult at first to try and figure out how exactly we wanted to do this. We decided on using rotational energy, which we had learned about this semester, to wind up a string, which will then raise our flag that is attached to the string. From there we used the other topics that we had learned to build the beginning and the end. One of our first ideas was to use a spring loaded cannon to shoot a marble, which would begin our device. This idea did not make it past the planning phase, because there was not a practical way for it to be started by the team before ours. The end result from our planning was a strong design that was not too complicated, but did include many steps. The team before ours was to drop a weight, and which would pull a string and begin our device. Our device begins with a hot wheels car rolling down a track and striking a wooden block. This demonstrates conservation of energy as the car rolls down the track. When the marble hits the wooden block and starts a chain reaction like dominos, an elastic collision is taking place. As the wooden blocks fall like dominos, energy is transferred, but with some losses. The final block has a needle on it that pops a balloon, which is blocking a propeller on a dowel with potential rotational energy built up by a rubber band. When released the dowel turns pulling the string and raising our flag, like I have stated above. At the end of the dowel there is a small box containing another marble. When the dowel begins to turn the marble is released to fall onto a Popsicle stick balanced on a small piece of wood at its center of mass. The small distance that the marble drops from rest is an example of conservation of translational energy. The final step of our project is projectile motion with the ejection of the lego man from the opposite end of the Popsicle stick to hit a rod and begin the next team s project. When the hot wheels car starts it is at rest and at a height of meters. = h and when the car reaches the bottom of the track there is =. By using conservation of energy we found that the velocity of the car at the end of the track is /. By using the mass of the hot wheels car to be.3 kg we found that the energy of the car at the bottom of the hill is J. When the car hits the wooden block it creates and elastic collision, which can be represented by m 1 u 1 + m 2 u 2 = m 1 v 1 + m 2 v 2.

4 4 In this case the velocity of the wooden block is zero at the start and the velocity of the car is zero at the end. If the block s mass is twice as much as the car then the equation is =.6, where the velocity of the wooden block would be 3.35 /, equal to half of the velocity of the car. We wanted the block to tip over instead of just move in the direction the energy was translated, but we found this was not the case. At any rate, the block did begin a chain reaction, so the blocks translated energy to one another until the last one fell and popped the balloon. The balloon would not take much energy to pop, so it is ok that the blocks observe some losses. After the balloon is popped the energy that has been built up by the rubber band is released. This energy results in a speed of 3 rev/sec for about 1 sec. This equals rad/sec, which equals a total distance traveled by the Popsicle stick propeller to be rads, according the constant angular acceleration equation, = /. After the dowel begins to spin, it releases the marble to drop meters from rest. By using the constant acceleration equation, = ᵢ +2 ᵢ, the velocity of the marble when it hits the Popsicle stick knocking it off its center of mass can be calculated. = Velocity equals 1.46 /. By using the trajectory equation ₒ = ₒ ₒ 1+tan ₒ we can find the angle of trajectory. vₒ= 1.46 m/s, x=.0508 m, xₒ = 0 m, and yₒ =.0254 m. By plugging in these numbers you can find that the angle is 3.6. The materials for our project were not hard to find. This is a chart that shows the materials we used and how much they cost. Materials Quantity Price Small Dowels 1 bag $2.50 Hot Wheels Track 1 bag $2.50 1" Wide Pine Board 5 ft $4.00 Marble 1 Popsicle Sticks 10 Water Balloons 1 bag Rubber Band 1 Thread 2 ft UT Flag 1 Lego Man 1 Needle 1 Hot Wheels Car 1 Total $9.00 We found that we already had most of the materials lying around our dorm rooms or houses. The only items necessary to purchase were the dowels, hot wheels track, and pine board. This came to total around $9.00. In the end our project turned out very well. I figured out that I should have used wood glue on the propeller and not hot glue. After our presentation, the project went off with no problems. I did notice the balloon that was used to create the motion of the towel was beginning to fall apart

5 because of all the trial runs. When we got to the part where we tried to start other peoples we had problems. It did not work very well in a circle. The way we had it planned to start the other peoples didn t work, neither did them starting ours. If I could do it again I would make sure that our team collaborated with the other teams better. I would also have reset everything that could break before the actual testing date. It would also be better to use wood glue on stuff that could break easier. In the end we learned a lot about teamwork and how to apply knowledge. 5