The 360 Gram Light Popsicle Stick Bridge [How to & Analysis]

Jared Frank; Aneesh Lodhavia; Alex Shortt

Period 4

Intro & Specs

Our assignment was to build a bridge 20 cm tall, and 60 cm wide. The two bases touching the ground have to be no wider than 5 cm, and there needs to be an open space under the bridge 10 cm tall and 50 cm wide. [Figure 6] The bridge cannot weigh more than 454 grams (about one pound) and needs to carry at least forty times its weight and the center of the top before breaking.

Build Strategy

Our first idea going into the build process was to make as many triangular shapes as possible. According to common knowledge, the strongest shape in the natural world is an equilateral triangle, so it makes sense to incorporate as many triangles into our build sketch as possible. We ended up using equilateral triangles as our side, supporting the bridge roadway at the top [Figure 5]. Regarding the base, we simply tried to layer Popsicle sticks enough to pass the 20 cm height expectation [Figure 2]. We reinforced the base with vertical X-shapes, connecting the sticks together, thus dispersing the weight equally to each stick of the base. We also connected the left and right sides of the base with a single stick, preventing the diagonals of the rectangle created by the base to shift in length [Figure 5]. When putting it all together, we took a unique approach to connecting the side to each base. We stuck the end Popsicle sticks into the top half of the bases, and laid the bottom of the ends of the side on sticks resting on the top half of the base. To prevent the side from detaching from the base, we put anchor sticks on top of the other side of the stick mentioned above [Figure 3, 4]. At the end of the build, we had a choice to either glue the roadway to the side supports or leave the two sections of the bridge unglued. We chose to leave the two unglued because we believed that the initial space between would allow the side supports to carry less weight.

Data

Weight of Bridge: 360 grams (0.8 lbs.)

Weight held by Bridge: 75 lbs.

Weight Ratio: 94.9%

Video of Weight Test: https://www.youtube.com/watch?v=r5gEwAo49VM&feature=youtu.be

Analysis

Our goal was to hold 100 times the weight of the bridge; we fell short of the goal, holding around 95 times the weight. Using the weight test, we discovered that the bridge broke in the middle, closer to the right; the side supports were mainly responsible for the damage. Looking back at our design, we realized that our supports were under-reinforced. We could have either added extra sticks throughout the depth of the bridge or used a cross-x design, rather than an equilateral triangle design. Either way, any assistance to the side supports would have saved us an extra ten or so pounds, giving us the reach we needed to achieve the 100 ratio goal. Although we are not able to know when the base would give, it is safe to say the base was the strongest part of the design. The base did not give way before the side supports, and looked stable during the crash of the bridge. We could have used the extra 90 or so grams (the weight limit of the bridge was one pound, or 454 grams) to solely add extra reinforcement to the side supports. Also, we could have added extra reinforcement under the roadway [Figure 1] by adding sticks perpendicular to the roadway, especially in the middle.

Sketches

Capture

Jobs

Jared: Bases; Connecting the pieces together; Blog; Video

Aneesh: Side Support; Blog Edits

Alex: Roadway; Blog Edits; Weight Tester

Pictures & Figures

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Figure 1 (Bottom Side Up)
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Figure 2 (Left Side View of Left Base)
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Figure 3 (Right Side View of Left Base)
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Figure 4 (Back Side View of Left Base)
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Figure 5 (Bridge without Top Roadway)
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Figure 6

The Arturo Rocket

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Jared Frank, Vince Feliciano, Arturo Gamboa-Gonzalez

Period 4

AP Physics 1

Bottle Rocket Lab

Part 1: Pre-Experiment

  1. Materials & Procedure – List everything used! Include pictures! How did you construct your rocket?

Materials:

  1. 2 2-liter bottles
  2. Cardboard
  3. Duct Tape
  4. String
  5. Marshall’s Thin Bag
  6. Ziploc Bag
  7. Orville Popcorn
  8. Hard-Boiled Egg

Procedure:

  1. Cut a 2-liter bottle in half, around the diameter. This will act as the egg capsule.
  2. Cut out 4 fin-shaped cardboard pieces, and attach them around the whole 2-liter bottle, each 90 degrees apart.
  3. Smooth any rough edges on the fuel cell with duct tape so that it travels upward easier.
  4. Fill a ziploc bag with popcorn. Place it inside the capsule.
  5. Cut the Marshall’s thin bag so that it can act as a parachute for the capsule.
  6. Tape one side of the thin rope onto the edges of the parachute, the other onto the edge of the capsule.

Part 2: Experiment

https://youtu.be/A8YJksani-I?t=1m38s

Data:

Note: Because our rocket flew higher during our first launch when our video file didn’t work, we used the initial velocity and mass values for that launch in our data; the time values, however, come from our second launch shown in the attached video.

Time from rest to acceleration (2nd launch): 0.24 s

Time from acceleration to peak(2nd launch): 1.30 s

Time from peak to ground (2nd launch): 4.20 s

Initial velocity (1st launch): 53 km/hr = 14.7 m/s

Mass (1st launch): 1.129 kg

FBDs:

Left FBD is the rocket when it lifts off the ground, right FBD is the rocket when it starts to fall down.

  1. Results – How did your rocket perform? Be specific, Compare with others, What factors (weather, user error, equipment malfunction) were present?

Results: Our egg ended up flying 37.4 feet. Our rocket separated at 1.54s, and as the body of the rocket barrelled down, the nose cone with the egg slowly glided down at -1.28 m/s^2. This acceleration is significantly less than that of gravity, -9.8 m/s^2, which goes to show how successful our parachute was in creating enough drag to slow the nosecone down enough to protect the egg. The cushioning from the popcorn also reduced the effects of the impact on the egg, leaving our eggonaut unharmed!

Error: As noted earlier, we combined data from two different launches, which most likely resulted in values different from the actual height and time of the launches. Our rocket’s low height compared to our initial launch (in which our video file didn’t work) can most likely be attributed to the different rocket launcher. Many of the groups who launched rockets before and after ours also didn’t quite reach the height other groups had reached with a different launcher a few days before. In addition, our rocket might have separated too early because the nose cone was placed on top of but not attached to the body, which meant that the momentum resulting from the initial thrust force was distributed between the nosecone and the body too early.

Part 4:  Conclusion – What could have made your rocket better? Size, Shape, Weather, What would you change?

To make our rocket perform better, our group should have lengthened our rocket to ensure more stability. During our launch, our rocket tilted to the side a little bit, so if the rocket stayed completely upward, it most likely would have traveled higher. In addition to the length, we could have patched the rough edges on our rocket better. Without the rough edges, we would have neglected a lot more air resistance, so the acceleration would have been closer to -9.8. Regarding the egg, we protected our egg pretty well, as it survived every launch.