Balloon Rocket Experiment (page 2)

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Author: Alex Jacobsen
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Summertime Science


All rockets work by shoving gas out of their nozzles really rapidly. This pushes the rest of the rocket in the other direction, as predicted by Newton’s Third Law: “For every action there is an equal and opposite reaction.” What this means is when you push on something, it pushes back on you just as hard. You might then think “Why don’t I fly all over the place when I push on something or throw a ball?” The main reason you don’t go flying like your ball is because you weigh more than it does. Even if the ball pushes back on you with the same amount of force that you apply to it, you’re a whole lot harder to move!

The bigger balloons move farther because they can push more air. While all of your balloons pushed air out at roughly the same speed, the bigger balloons had more “fuel,” allowing them to exert force for a longer period of time.

It’s not too hard to calculate the amount of air in each of your balloons. This equation will help:

Balloon Rocket Volume Equation

Another cool thing is that the direction of the push matters quite a bit. Try taping your balloon so that its nozzle points to the side a little instead of straight along the straw. What happens? Can you match a bigger balloon and a smaller balloon together so that they don’t go anywhere when you let them loose? Space stations use this principle to turn end over end, spin, or even move sideways. It’s the only way they can change what direction they’re pointing, because they don’t have anything else to push off of.

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