Physics
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Bottle Rocket

Bottle Rocket

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When we think physics, we might picture a boring classroom with formulas scribbled on a chalkboard. But it doesn't have to be that way! You can actually perform thrilling experiments to learn about physics. You don't have to memorize equations either, there are other ways to learn. You can step outside and witness concepts in action. Building a bottle rocket is a perfect example of this. It's a fun project you can do at home that shows how Newton's three laws of motion work in real-life situations. So, why not give it a shot and launch your very own bottle rocket?
When we think of physics, we often think of an old classroom with formulas on a chalkboard. But there are many exciting experiments we can do to learn! Building a bottle rocket is a great way to demonstrate how Newton's three laws of motion work in real-world situations. It's a fun home project that can help you understand physics concepts in action.

Bottle Rocket Explanation

Building a bottle rocket is simple and fun! Follow these steps to create yourItems needed:

  • One plastic bottle, around 60 ounces
  • One cork that fits snugly into the bottle entrance
  • One pump with a needle adaptor and a long line
  • One sheet of cardboard, something to cut it, and glue
  • Water

Instructions:

  1. Cut out 2-5 side fins from your cardboard and stick them to the side of the bottle near the cap. Make sure they're evenly spaced apart.
  2. Create a cone from the remaining cardboard by cutting out an isosceles triangle, then sticking the two shorter sides together. Attach it to the side of the bottle without the lid, with the tip of the cone facing away.
  3. Pierce the cork with the needle adaptor end of the pump. Make sure the needle goes clean through the cork.
  4. Remove the bottle lid and fill it about a quarter of the way with water.
  5. Push the cork into the hole in the bottle, ensuring it's a tight fit.
  6. If your fins allow, stand the bottle on its own, otherwise use something to hold it upright with the cone pointing towards the sky.
  7. Carefully remove the pump from the rocket, making sure not to knock it over.
  8. Find an open space such as a field or empty parking lot to launch your rocket.

That's it! Your bottle rocket is now ready to launch. Have fun and stay safe!

One example of a bottle rocket. Note that yours may look different, depending on how you customized it
One example of a bottle rocket. Note that yours may look different, depending on how you customized it

To use the bottle rocket, pump air into it until the bottle rocket suddenly flies away! Hopefully, you get it high into the air!

What are the Forces that a Bottle Rocket Experiences?

So, why does the bottle rocket take flight when you fill it full of air? When you pump, you add more air into the bottle while the bottle still has the same volume. By doing this, you’re increasing the pressure inside the bottle, which is exerting a force on the inside of the bottle. Eventually, when this pressure becomes too much for the bottle to handle, its force will push on the cork enough to rapidly eject it from the bottom of the bottle.

The sudden release of pressure due to a new opening in the bottle will push all of the air out of the bottle as quickly as possible. When the air exits the bottle, it pushes out all of the water alongside it, with the force that was previously pressurizing the bottle. With the water moving at this velocity, it will, in turn, provide this same force in the opposite direction to the bottle, causing it to fly up with a force equal to the force exerted on the water.

The fins and cone we added to the rocket act as stabilizers, keeping the rocket in the same position as much as possible, achieving a uniform flight path. They also help to minimize air resistance, allowing the rocket to fly even higher. These reasons also explain why we need to space the fins equally apart. If they were uneven, one-half of the rocket would have more fins on it, making one-half weigh slightly more. This causes instability and will prevent the bottle rocket from moving straight up. Instead, it will move in the direction the heavier side is facing.

This diagram shows the forces that a bottle rocket will experience as water is expelled from it, as well as labels showing where everything on a bottle rocket should be. Science World

Bottle Rockets and Newton’s Laws of Motion

This bottle rocket project will demonstrate all three of Newton’s laws of motion.

Bottle Rocket Inertia

Newton’s first law shows us that when the bottle rocket is initially at rest, it will remain stationary until a force is exerted upon it. In this case, the pressure released within the bottle is this force.

Bottle Rocket Force

Newton’s second law is shown through both the mass and the acceleration of the water as it shoots out of the bottle. Therefore, the acceleration of the water will be equal to the force exerted by the water divided by the mass. Because of this, if we add more water, we can potentially increase the distance the rocket travels, as adding more water means increasing our value of mass, which will, in turn, increase our value for force. The formula looks like this:

Bottle Rocket Action and Reaction

Another example of a finished bottle rocket, this time decorated! This one has the lid at the top and the bottom cut out instead, but it will work the same way. Pinterest

Building a Bottle Rocket - Key takeaways A bottle rocket is easy to make and fun to use. It will use water and air pressure to propel itself high. A bottle rocket demonstrates all three of Newton’s laws of motion.

Bottle Rocket

How does a bottle rocket function? 

 A bottle rocket functions by propelling water out of the bottom by increasing its internal air pressure. The water will then use Newton’s third law of motion to exert that same force onto the bottle rocket, sending it high into the sky. 

How do bottle rockets use Newton’s laws?

A bottle rocket uses Newton’s first law by remaining at rest before applying any forces. It demonstrates Newton’s second law that the force exerted on the water is equal to its mass and acceleration. Finally, it shows us Newton’s third law through the bottle rocket having the water’s force exerted onto itself, equal in magnitude but opposite in direction.  

How to make a bottle rocket? 

To make a bottle rocket, you need to attach a cork with a pump to the lid so that air can be pumped inside. Putting water into the bottle and fins and a cone onto the bottle will turn it into a bottle rocket. Pump air into the bottle until it takes off.

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