What is it about balloons? It doesn’t matter how old the kid is, you bring out a balloon, just the regular kind that you fill with your own CO2 ,  and the is an excitement in the air. My two-year old loves hitting balloons in the air, trying to keep it up as long as possible. The 7th grade students see a pack of balloons on my counter, and immediately are wanting to know if they will get to blow one up!

Good thing this time the answer was yes!

We have been wrapping up our study on Newton’s Laws. I wanted an activity that would require students to use their knowledge of all three laws in their design. A balloon rocket car fit perfectly. I based my design after what I saw here at kidzworld.com, however there are many variations to this activity using other materials!

Goals of the design:

  • Students were to design and create a “rocket car” that used the balloon to thrust the car forward.
  • Students needed to calculate the momentum of their car, and therefore find the velocity.
  • They measured the distance the car went and the time it took to go that distance.

Here are the materials that you need:

  • Styrofoam
  • Cardboard
  • Straight straws
  • Flexible straws
  • Wooden skewers
  • Bottle caps with a hole in them (used as wheels. You can easily make a hole by hammering a nail lightly through the center of the cap. I also had wooden wheels on hand, so I let the students choose which they wanted to use.)
  • Balloons
  • Tape
  • Scissors

Though the basic design of the car was going to be the same, there were several smaller choices students could make that would affect how well the car worked. For example, they could pick either cardboard or styrofoam to be the base of the car. Either wooden wheels or bottle caps could be used for the wheels. The wheels were attached by the skewers and/or straws underneath the base of the car. On top, a bendy straw was attached. At one end, students needed to secure the balloon. The other end was left open so someone from the group could blow the balloon up and be ready to race!

This car went the farthest. The group cut pieces out of the side to eliminate extra mass.

I allowed students three trials. Some had cars that moved fast, but not far. Others moved slow and steady and still others moved at all. If I had one more day to do this activity, I would have allowed them to change one thing about their designs to see if they could make their cars go farther or faster.

After their testing, recording and calculating of velocity and momentum, we discussed how Newton’s laws were involved.

Newton’s 1st Law

An object in motion stays in motion unless an unbalanced force acts upon it. Students understood this through the slowing down of the car from the friction. They also stated that if the car had more mass, that meant there was more inertia which made it harder for the balloon car to start moving.

Newton’s 2nd Law

F=ma. A more massive car would be harder to accelerate with the same force. Students figured out that more massive balloon rockets required much more balloon air power to get going. To increase acceleration, those balloons needed to be blown pretty big!

Newton’s 3rd Law

For every action there is an equal and opposite reaction. The application of this law was fairly obvious to the students. They immediately realized that the force of the air coming out of the balloon from behind would push the balloon rocket forward with an equal amount of force!

The students love comparing their balloon rocket cars and would have loved a race! Maybe next time I can turn this into a Newton’s Laws tournament!

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