Bottle rockets

Challenge: To design a bottle rocket that will hit a target on the main field.

Parameters: The bottle rocket must have one unmodified 2L pop bottle as the pressure vessel, to which Mr. J will glue a flow restrictor (so it can be launched by my launch device). Fins, fairing, fuselage, nose-cones, etc. must by taped to the pressure vessel and cannot damage it in any way. The nose cone cannot be sharp, and the fins cannot be made out of sheet metal for safety reasons.

Scoring: You will be shown the target location and will have two attempts to hit the target. The target location will be somewhere between 60 m and 80 m from the launcher. You will be charging your rocket with 100 psi air from a compressor, and will be aiming the launcher by yourself. Your best attempt will be used for the score.

Score = (∆x / x) * 100%

x is the position of the target measured horizontally from the launcher.

∆x is the distance between the target and where your rocket lands.

Rank will be based on score, with lowest score earning highest rank.

Physics: Unbalanced force applied by the compressed air on the escaping water causes an equal and opposite force on the pressure vessel. The rocket will accelerate according to Newton’s Second Law. The force is proportional to the air pressure and varies as the rocket accelerates, decreasing during the launch. The mass of the rocket also changes as water is expelled, which improves acceleration, so the acceleration is definitely not uniform. After it runs out of water, the rocket will experience unbalanced force due to the forces of gravity and air drag. The force of drag decreases as speed decreases, so again, not uniform acceleration. After your first launch, you can try changing the angle or the amount of water you put in the rocket to make it get closer to the target on your second attempt.

Extensions: Physics modelling software can handle all the variables mentioned above, and you may be able to find someone who has already done that work online because this is a very popular project!

Help/Hints: Too many to mention here, but pay attention in class! You will need lots of 2L pop bottles, tuck tape, fin material, and playdoh or plasticine.

Quiz Topics: Constant Acceleration in One Dimension, Intro to Projectile Motion.

Newton’s Laws. (Unbalanced Forces Cause Acceleration)

Online Text: ch 2, ch 4, ch 5 (one dimension and intro to two)