Bottle rocket launchers can be a great way to increase interest as your class kicks off this Fall. We’ve collected some tips for how to get more out of these rocket powered demonstrations and launch your students into the world of force and motion in full Cool Stuff fashion.
Hold a friendly contest to engage interest in what affects the behavior of the bottle rocket during flight. Form the students into groups and then provide them with a variety of cardboard tubing options and some extra cardboard to cut out fins. Actual construction of the rocket may be something you have them do outside of the classroom. Don’t jump into the Physics quite yet. Just challenge them to discuss and consider a variety of elements when constructing the rocket, such as length, size of fins, weight of rocket, amount of water in the rocket, and amount of pressure used during the launch (not more than 40psi of course!). Then hold a contest where the goal can be to see which rocket stays in the air the longest, which one reaches the highest, which one can carry the most weight, or which one provides the most accuracy in landing closest to a specific spot. We’ve found that the duration of flight is the simplest activity to measure, but we’ve provide some suggestions below if you would like to introduce altitude as well. After the results are in, now you have a perfect opportunity to turn their interest into an engaging discussion about force and motion, describing what elements resulted in the various outcomes and why.
The primary factors for improvements in speed and stability are the different levels of pressure, the amount of water in the bottle, the overall weight of the bottle, the length of the rocket body, and the addition of fins. With all of these variables, your students can experiment for hours, using this hands-on activity to gain a deeper understanding of a variety of core force and motion principles. For example, note the relationship between the amount of water expelled and the altitude reached. By throwing water in one direction, the rocket is thrown in the opposite direction. According to Newton’s Third Law, water and rocket should have equal and opposite momenta. How is this observed with this real world activity? Other observations that you can make include testing the bottle without water (using only air) or adding more water in the rocket than the air can expel.
Note about safety: The launcher shown in the video, the Super Bottle Rocket Launcher, has a safety valve to limit the pressure to 60 psi. The other launchers that Arbor Scientific carries do not have this feature. Please be sure to take precautions to always use a pump with a pressure gauge and do not exceed 40 psi. And of course, always make sure the bottle rocket launching base is firmly in place and not pointed at anyone. Other safety precautions include setting it up away from buildings, other structures, trees, telephone wires, and cars (when using the bottle rocket launchers in a parking lot). It must always be launched straight up in an area with no overhead obstruction. This can be a very fun and safe activity, as long as you take the proper precautions!
How to Measure the Altitude
As we mentioned, duration of flight is really the simplest way to provide a more accurate comparison of bottle rockets. Altitude is another great option, but there are some limitations to be aware of, especially when doing this in a contest setting. Depending on how you measure the altitude, it may be difficult to obtain precise measurements. For example, if you are measuring the altitude from one ground position, you may have less accurate results due to the horizontal movement of the rocket as it launches, which can vary based on which test you are running affecting where the actual rocket launch base is (which effects the altitude equation when using the angle and the distance to the base). Teachers have found success with having multiple students taking the measurements at each ground location, throwing out measurements that were obviously wrong and then averaging the rest. You can also measure altitude from multiple ground locations equidistant from the rocket launch base (launch pad), such as opposite sides of the bottle rocket launch pad. That allows you to factor for horizontal movement more accurately. With this method, you’ll need a sheet of graph paper with a chart that places the bottle rocket launch pad in the middle and then you mark down on the x-axis how far the first group is from the base. The altitude will be measured vertically (in the y-axis). The second group should be the same distance in the opposite direction. On the chart, this is represented on both ends of the x-axis. You’ll need a way for the students to measure the angle of the bottle at its highest point.
Note: Arbor Scientific's Altitude Finder provides an easy way to measure the angle that a bottle rocket reaches at the top of their flight.
Once both groups have come up with a consensus of what angle they measured from their ground location, you can then transfer these angles to the graph using a protractor. Where they cross will tell you how high the bottle went based on the y-axis.
Here is an example of the chart with further instructions that you can use to measure altitude with two groups of students:
If doing this as a contest, even a friendly one, it is helpful to take these extra measures to ensure the fairness of the competition.
More Math Please!
For a way to measure altitude that involves slightly more complex mathematics, you can create your own rocket altimeter. You will need to mount the chart we provide on a sheet of cardboard with a plumb line attached to one corner. Below, we provide a set of thorough downloadable instructions that includes the worksheet that is used for measurement and how to calculate the altitude based on your measurements. Simply print off as many copies as you need of the last page of this document:
Note that you’ll need a piece of cardboard to attach to the back of each sheet you use for measuring altitude. You may want to create more than one for a larger class. You’ll also need a common pin (for poking holes in the cardboard), a string to use as a plumb line, a piece of tape for securing the string, and a weight for the end of the string (typically a large washer). You might also want a soda straw to use as a sight tube.
Unfortunately, this method does not account very well for horizontal movements of the rocket and cannot be combined with measurements from different vantage points, making it somewhat inaccurate when using in a contest setting. Therefore, we recommend to only use this approach when demonstrating the mathematic principles it uses while gaining a general sense in the difference between using different variables.
Super Bottle Rocket Launcher
The one piece bottle rocket launcher that can launch a 2-liter soda bottle up to 100 feet! What better way to provide students with a real-world application of the scientific method than to design, build and launch bottle rockets!
Bottle Rocket Launcher
With a plastic soda bottle, a poster tube for a nose cone, and some cardboard, you can create your own rocket. Then just added a little water, compressed air and launch!
Double Bottle Rocket Launcher
Launch two rockets at once! It's great for racing your students' rocket designs and you can also use it to test variables directly against each other.
Air power projectile
Explore projectile motion with this 100% safe, chemical-free air-powered projectile. Flies straight and true with minimal wind effect and with a consistent, repeatable initial velocity - important for students testing predictions.
Calculate altitudes, using triangulation, of objects such as our Air Powered Projectile and Bottle Rockets.
Stop Watch Timer
New Digital Stopwatch and Timer captures elapsed time to within 1/100th of a second and lap time.