Science Fair Guide: Straw Rocket
In addition to the straw rocket materials, you’ll need a tape measure and craft foam.
Ask a Question
What amount of added mass causes the rocket to fly the farthest?
Air is made up of countless molecules: oxygen, carbon dioxide, etc. When these molecules bump into moving things, it slows those things down. This is a force called drag.
Flying things – like the straw rockets – need some mass to overcome drag. Mass is just how much matter (like molecules) is grouped together in an object. For example, a marble has more mass than a piece of popcorn. An object with more mass can more easily push past the air and resist drag.
If there's too little mass, then the drag will slow down the rocket before it’s travelled very far. However, too much mass, and the rubber band won’t be able to supply enough energy to get the rocket moving.
One last piece of information: a standard 4" mini glue stick weighs almost exactly 4 grams.
Make a Hypothesis
Using the information above, make an educated guess about how much mass will work the best. Your hypothesis should be a simple statement, such as: “5 grams of mass will cause the rocket to fly the farthest” (This is not necessarily the best hypothesis; it’s just an example).
Conduct an Experiment
Create one straw rocket, but don’t add any mass, like a piece of a hot glue stick, to the tip yet. Build the fins out of craft foam. You’ll be reusing this rocket quite a few times, and foam is much more durable than paper. You may want to make a second, identical backup rocket in case the first one gets too damaged.
Without any extra mass added, launch the rocket straight forward three times and record the distance travelled with a tape measure.
Add a very small amount of mass (hot glue stick) to the tip. About a ½"-long piece is a good place to start. Launch three times again.
Remove that glue stick, and add a piece that’s ½" longer, then launch three times again.
Repeat until an entire 4"-long glue stick has been added to the rocket.
Setup the Controls
Controls are measures put in place to prevent unintended things from affecting your results.
Follow these procedures to ensure your data is accurate:
Stretch out the slingshot’s rubber band with your hands before beginning. The rubber band loosens quite a bit when it’s first used. Pre-stretching it will help ensure that each shot uses the same amount of energy as the one before it.
Make sure to fire straight ahead each test. Avoid aiming even slightly up or down.
Make sure to pull back the same amount for each test. Optional: Attach a ruler perpendicularly to the slingshot so you can pull back a precise amount each test.
After each test, inspect the rocket for damage. Make only the smallest repairs necessary. Avoid replacing fins or adding extra tape! These things can have a big effect on how far the rocket flies.
If you mess up a test (e.g. the rocket hits the slingshot when launched), then discard that result and test again. Record any discarded tests, and write a note about why you decided to retest.
Launch the rockets when it’s not windy.
Record the distance of each test. When finished, add up the results for each amount of mass added, then divide by 3 to get an average distance. For example, if a rocket with the mass of ½" of a glue stick flew 121", 102", and 93", then 121+102+93 divided by 3 is an average of 105.3".
Your data might look something like this (this is not real data; don’t use in your conclusion):
Describe any additional observations you made during the experiment. Be sure to include things might have affected your results such as launching errors, wind during some tests, or anything else unexpected.
Look at your data and conclude which amount of weight caused the rocket to fly the farthest.
Present your main conclusion in a visual form, such as writing the average distance flown next to each piece of glue stick, and creating a graph that shows the distance the each one travelled.
Summarize your hypothesis, experiment method, the controls you put in place, and your raw data.
Write your conclusion, and explain why you think the results are the way they are.