Bottle Rocket: Newton's Three Laws Of Motion

Background:

Bottle rockets are great models to examine Newton’s three laws of motion. The bottle rocket will remain on the ground until an unbalanced force, water, thrusts the rocket upward. This is defined by Newton’s first law of motion: an object at rest stays at rest or an object in motion, stays in motion (in the same direction/at the same speed) unless acted upon by an unbalanced force. It is also known as the law of inertia.

The more mass the rocket has, the less acceleration it will have using the same force. By adding a small amount of water, the force will increase. This can be described by using Newton’s second law of motion: the net force of an object is equal to the product of its mass and acceleration.

When the bottle rocket

is pushed upwards, the water is pushed out of the bottle backwards, creating an equal and opposite reaction force. The air pressure inside the water bottle rocket pushes downward against the water while the water pushes backwards against the trapped air. This is how the rocket takes off. This is displayed by Newton’s third law of motion: for every action, there is an equal and opposite reaction.
Data:
The amount of water put in the bottle was 800 milliliters. Three fins were used on the bottle rocket. The time of flight of the bottle rocket was 3.01 seconds with the parachute deployed.
Analysis:
The rocket, when launched, flew in an arc. When the parachute deployed, it did benefit the bottle rocket a little, but it didn’t help too much. Changing one of the indirect variables can affect the time of flight. The more water added into the rocket, the shorter flight time it will have because of the increase of its mass. Having four fins on the bottle rocket might create more drag and more weight on the rocket which, in conclusion, will decrease the time of flight.
Conclusion:
In conclusion, if the amount of water placed in the bottle rocket increased, the flight time will decrease. It is because there will be more weight added onto the rocket which will prevent the rocket from slowly falling down. With too little water, there would be a small amount of reactive mass to throw the rocket upwards.
Making the parachute larger would decelerate the rocket coming down because the air resistance (drag force) prevents the rocket plummeting, so the bigger the parachute, the slower the rocket will fall. For instance, a skydiver always has a parachute attached to them. Without it, the skydiver would die from falling. As the air pushes into the parachute, it creates a force opposite to the force of gravity, slowing the skydiver. This relates to the bottle rocket and the parachute.
Additionally, three fins on the water bottle rocket will stabilize the rocket when launched in the air, and create less drag.

Overall, changing the indirect variables (amount of water and the number of fins) can create huge effects on the direct variable (time of flight).

Reflection:

What worked or didn’t work and why?

The parachute of the bottle rocket deployed. It worked because it wasn’t “stuffed” into the nose cone. If it was, however, it would be stuck in the nose cone and not deploy. Even though the parachute deployed, it didn’t help the rocket decelerate too much. It was most likely because the parachute wasn’t big enough. If the parachute was made larger, the time of flight for the rocket would’ve increased.

What did you find compelling?

The most compelling part of this project was when the parachute deployed. I wasn’t sure if the parachute would deploy or not. Before I launched the rocket, I made sure to put the parachute loosely in the nose cone so when the nose cone came off, the parachute wouldn’t be stuck in it. As the rocket launched, I was very excited!

What, if anything, would you change next time?

The size of the parachute was a little small, so next time I think I should make the parachute larger. It would as said before, slow down the rocket more

gradually.