Balloon Rocket Car Project STEM Activity

Propulsion And Newton’s Third Law

Every day, we bear witness to the marvels of motion and energy.

Airplanes cut through the atmosphere, ships traverse the vast oceans, and rockets propel upwards into space.

But have you ever wondered how these vehicles achieve those movements? 

These movements all have one thing in common — thrust.

In airplanes, for example, the engines generate thrust by exhausting gases from the back. A reaction thrust is produced in the opposite direction, propelling the airplane forward.

This same principle applies to ships, where engines create thrust by expelling water in one direction, leading to a reaction force that pushes it in the opposite direction.

Rockets utilize a similar concept by combusting fuel and oxygen to produce hot exhaust, which is expelled and generates a thrust that propels it into space.

The fundamental concept that governs the similar motion of vehicles on land, water, air, and even space is propulsion.

Studying propulsion and Newton’s Third Law of Motion helps us to understand how airplanes, ships, and rockets translate energy into movement.

Newton’s Third Law of Motion states that for every action, there is an equal and opposite reaction.

In simpler terms, when a force is applied in one direction, an equal force pushes back in the opposite direction.

This principle is the driving force behind propulsion and is tremendously significant when applied to vehicles, as it explains how various forms of energy result in motion.

In this Balloon Rocket Car Project STEM Activity, we will closely examine Newton’s Third Law of Motion in action by designing balloon-powered cars and observing how the potential energy in inflated balloons is converted into kinetic energy to set the cars in motion.

Now, are you ready for our Balloon Rocket Car Race Challenge?

Balloon Rocket Car Race | STEM Experiment

Balloon Rocket Car Race | Propulsion STEM Activity

Prep Time: 30 minutes
Active Time: 30 minutes
Total Time: 1 hour

Here is a fun science experiment to show how propulsion creates thrust to move vehicles.


  • a toy car(s) (You can also build one yourself. One of the cars we used was a Lego car)
  • a balloon
  • a drinking straw
  • a rubber band
  • packing tape


  • adult supervision


  1. Insert one end of the straw into the balloon and fasten it using a rubber band.
  2. Secure the balloon onto the toy car. The balloon's opening should point towards the back of the car.
  3. Blow into the straw to inflate the balloon and hold the straw tightly when you're done to not let the air escape.
  4. Put it on a table or the floor and then let go.balloon attached to toy car and a straw


balloon attached to another toy car, when released, it shoots forward.

  • If your car doesn't move or moves very slowly, try a smaller, lighter car.
  • Experiment with cars of different sizes and weights and see which one goes the fastest.
  • Experiment with balloon nozzles pointing at different directions and see what happens.

balloon attached to toy car and straw.

3 balloons attached to top of 3 toy cars

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The Balloon-Powered Vehicles

The Balloon Rocket Car Challenge is a hands-on, engaging, and engineering design project that invites participants to craft, build, and race their balloon-powered cars.

By experimenting with different vehicles, sizes, and designs, participants can learn how various factors impact the performance of their balloon-powered cars.

The car’s design incorporates simple materials such as drinking straws, rubber bands, balloons, and cardboard to create a vehicle propelled by the energy stored in an inflated balloon.

Our propulsion system will consist of a basic balloon, which is made out of latex.

The inflated balloon stores potential energy due to the elasticity of the rubber material and internal pressure exerted by the air.

On the other hand, the un-inflated balloon has little to no potential energy, but when inflated, the potential energy increases as the stretched rubber contracts.

As the air is released from the balloon, the potential energy is converted into kinetic energy or the energy of motion. The force of the exiting air creates an equal and opposite reaction force, which pushes the car forward.

In this project, straws such as those used for milkshakes and smoothies play a crucial role. They serve as nozzles that control the release of air from the inflated balloon.

Both straight and bendy straw pieces can work, but the key is to ensure a secure seal, retaining the potential energy within the balloon until it’s time for the balloon race.

Use duct tape to attach the balloon to the vehicle body, which can be made from cardboard, a milk carton, or a water bottle.

This platform serves as the foundation for mounting our balloons, and creating our balloon-powered cars.

The car body is not limited to the materials mentioned above; feel free to experiment with the car’s design on paper before starting the project.

Whether you use corrugated cardboard or a delivery cardboard box, what’s important is that the vehicle body and chassis are light enough to be propelled by the balloon force.

For wheels, lightweight options like plastic bottle caps or jumbo paper clips can be attached using a strip of duct tape.

They serve as the contact points between our vehicles and the flat surface on which they will travel.

For surfaces, balloon rocket cars perform best on a smooth surface. Whether it’s a kitchen floor or a polished classroom tabletop, the smoother the surface, the less resistance there is to slow down your balloon racer.

But that doesn’t mean you can’t experiment with different types of surfaces. You can try the balloon car on an inclined or rougher surface to see how it affects the vehicle’s motion.


The Balloon-Powered Car Challenge demonstrates the transformation from potential (the inflated balloon) to kinetic energy (the energy of motion as the car moves).

Once the straw nozzle is opened, the stored potential energy is converted into kinetic energy, propelling the car forward.

This transformation and subsequent vehicle movements are visual representations of Newton’s Third Law of Action and Reaction.

When the balloon is blown up, the air inside is pushed on the skin to keep it inflated. Covering the straw opening keeps this high-pressure air trapped.

When the straw nozzle is uncovered, the balloon’s stretched skin pushes the air into a thrust.

This thrust force propels and makes the car accelerate forward. And you will find that the lighter the vehicle, the faster it goes.

This demonstrates Newton’s Third Law of action and reaction.

When there’s an action, like the balloon skin compresses the air pushing it to escape backward, there is a reaction, the resulting thrust into the balloon forward.

Likewise, in an airplane, the turbine engines use the surrounding air to generate a thrust that propels it forward. The surrounding air is the working fluid in this propulsion system.

In a ship, the turbine engines use water as the working fluid.

In a rocket, fuel, and oxygen are mixed and exploded in a combustion chamber to produce hot exhaust. This hot exhaust is the thrust that propels it.

Unlike airplanes, a rocket doesn’t use the surrounding air as the working fluid because there is no air in space.

All of these vehicles move by Newton’s Third Law.

The Balloon Rocket Car Project STEM Activity is an excellent opportunity for individuals to engage with essential concepts in physics, including propulsion, thrust, Newton’s Third Law, and the various forms of energy.

This exciting science project challenges creativity and problem-solving skills while providing insight into the practical applications of these principles in real-world contexts.

Whether undertaken as a  sixth-grade class activity, a science fair project, or simply as a fun project at home, the Balloon Rocket Car Project will inspire curious minds and spark a passion for the world of science and engineering.

Remember,  Newton’s Third Law of action and reaction is at the core of every movement around us, from electric vehicles on the road to rockets shooting off into space.

And, with a balloon, pieces of straw, packing tape, a piece of paper, and a bit of creativity, you can bring this law of motion to life on your tabletop.



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