Water Bottle Rocket PBrL

Intro

For this project, our Pre-Calculus class designed and built rockets out of 2L bottles. Groups launched the rockets to investigate projectile motion, utilizing physics, parabolas, and trigonometry.

Final ↓

Design Consideration

Base

My group members and I used an upside-down 2L bottle with the top of another bottle as our base. The base is rounded to reduce air resistance. We left the bottom bottle whole so that when the water launched the rocket, the pressure would be focused on a flatter surface that's relatively in the middle of the rocket. We taped the top of a 2nd bottle to the top of the rocket for aerodynamics - the rounded rocket nose would be able to cut through the air more easily.

Fins

We added 3 fins (each 120° apart) to our rocket for stabilization. We constructed them with cardstock and wrapped each fin with foil tape and duck tape. We made sure not to make the fins too wide to avoid more wind resistance.

Weight

We made sure to keep our rocket light so it could travel a greater distance.

Aesthetics

We waneted our rocket to look like what it represented, a functioning, successful rocket. We used blue and yellow washi tape as decoration and to cover up taped areas. We also made a window and drew an astronaut using washi, foil tape, and Sharpie. Finally, we added some rhinestones.

Launch

The rockets were filled with water halfway and then pumped with air before being released, the pressure sending the rocket into launch. Our bottle was approximately in the air for 7 seconds.

Finding Height using Trigonometry

Using Trigonometry, we were able to find the height of the rocket after launch by using the angle measured when looking at the rocket at its highest point, the height of the person measuring, and the distance from where they measured compared to the rocket. Then, we used tangents and multiplied 30 yards (1080 inches) by tan(68.9°) to get 2798.9 inches. We added the height of the person to that to get 2861.9 in or 238.5 feet as the height of the rocket at its highest point.

Finding Initial Velocity

To find the initial velocity, we used the equation:

final position=(initial velocity)(time)-(0.5)(32)(time)^2

The final position would be 0 because the rocket would be on the ground. The time is 7 seconds. When we isolated the initial velocity by itself, we figured out 112 was the initial velocity.

Height of Rocket Respect to Time

Using www.geogebra.com, we graphed the equation y=-(1/2)(32)x^2 + (initial velocity)(x), which represents the path of the rocket with its height and amount of time in the air (x) in mind.

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