Rocket Day Classroom Tie-In
by Kalée Tock
Let's get everyone psyched up for rocket day in class! Here are several sample classroom activities and demos. Many of them have the learning goal that "air is there." Air can carry weight, air takes up space, and compressed air makes our rockets go! Another activity is about how fins keep the rocket's flight stable. The goal for Rocket Day is to have a parent do a 30 - 40 minute rocket activity with each of the PACT classrooms. The activity could be as simple as reading a story with rockets in it for the younger grades. For the older grades, the parent could talk about the history of rockets (Goddard to Operation Paper Clip to Sputnik to the first man on the moon), or the physics of how compressed-air rockets work (see below). The demos and activities here are generally flashy, fun, and popular, and hopefully will give students a greater appreciation for what goes on behind the big boom of Rocket Day.
- Air can carry weight. Start by asking the class about air: find out what they think it is and what it does. Most students will think that the only important thing about air is that we breathe it. Then ask them if they think air could hold a person up off the ground. Students will say "no" (duh!). Take an empty 2-liter water bottle (or any empty plastic bottle with a screw-on top--I have done this many different descriptions of bottles, including a milk jug) and verify that it is indeed "empty" by opening it and holding it upside down. Then put it on its side on the floor and stand on it, or have a student stand on it. The bottle will crumple a little, but you will still be off the ground. At this point I generally get a little theatrical. "Well, if it's empty, then what is holding me up?!" Students will say "the bottle!" At this point, unscrew the cap. The air will whoosh out and you will sink to the ground. Say, "But look--if I unscrew the cap, then the bottle can't hold me up anymore! Was it the cap that was holding me up?!" Eventually, someone will figure out (possibly needing a little guidance) that the bottle was not empty--it had air in it, and though we routinely discount air as being "nothing" because it is all around us, it actually is something that takes up space and does stuff. It can, for example, carry weight.
- Air Cannon. I have made a couple of air cannons (which you are welcome to borrow, if you don't want to make your own) out of paint buckets with a hole cut in the bottom and a cloth attached across the top. Hit the cloth, and air comes whooshing out from the hole. Students will be amazed when you "hit" them from across the room with a poof of air! Or, if they are scared, just hold the air cannon in front of yourself and hit it backwards--they will see your hair fly up as the air poofs you!
- Air can propel things. Air can also propel things, like rockets. To demonstrate this, blow up a balloon without tie-ing it, let go, and show how the balloon whizzes around the room with its "thrust" provided by the air you used to blow it up. If you want to get fancy, you could take the same two-liter bottle from the previous demo and attach its neck to a pipe with a bend in it so that the bottle is on its side on the ground and the pipe is sticking straight up. Put a paper-towel roll with one end taped over (or an actual rocket, made according to the instructions at http://web.tock.com/rocket/rocket.html) on the end of the pipe, and have a student jump on the bottle to blast it off. This home-made "stomp rocket" shows that the air in the "empty" bottle can actually make things go.
- Air takes up space. Place a wad of paper towel in the bottom of the clear cup. Turn the cup upside down and push it straight down into the deep container of water. The paper towel stays dry. Water cannot fill the glass because it is already filled with air. But if the cup is tilted, some air escapes and water can then enter.
- Air pushes on things. Fill a small cup all the way to the rim with water. Place a square piece of cardboard over the cup making sure there are no air bubbles trapped inside the. Holding the cardboard in place, turn the cup upside down. Take hand off cardboard. The cardboard does not fall. Air is pushing up keeps the card board and water in place. Because air pushes in all directions the cup can even be turned sideways and the water won't pour out. The index card prevents air from having a path for getting through the water to the top of the cup, so for the water to come out would create a vacuum in the top of the cup.
- Air has weight. This is from here and here. I have yardsticks that you can use, plus some thin pieces of cut wood that also work for this demo. Place a thin yardstick on a flat table with a little less than half of it hanging off of the edge of the table. Place a sheet of newspaper over the yardstick flat against the table (have as little air as possible under the paper) so that the fold line of the newspaper is at the yardstick. Quickly strike the end of the yardstick hanging off the edge of the table. If you strike it quick enough, the yardstick will break near the table edge. What's going on?
|The Earth is covered in a layer of air that is nearly 80 miles thick and at sea level (the bottom) exerts or 'pushes' almost 15 pounds of pressure per square inch. That means that a full sheet of newspaper laid out flat has nearly 9,300 pounds of air above it. When you break the yardstick above, you are able to break it because of that 'heavy' air pushing down on the paper while you quickly strike the yardstick. Initially, the table is pushing back on the paper, and if you move the yardstick quick enough, other air around the edges of the paper can't get under the paper fast enough, so you are trying to lift that 9,300 pounds with the yardstick! Some air gets under the paper, but not enough, so the yardstick breaks. (Mess Factor: Not much mess, but you need to be careful not to use too thick of a yardstick, it should be about 1/8 of an inch thick, but not more. Also, don't have a friend stand right above the yardstick when striking it as the yardstick or a piece of it could hit them in the face.) |
- Stability of Rocket flight. What does it mean for something in motion to be "stable", like a car or a bike? If it wobbles a lot, that is a clue that it is not stable. Why would something wobble? In general, for an object in motion on the ground, a larger "support base" leads to less wobbliness. In the case of a rocket, the fins are what stabilize the rocket's flight. For the main activity, we break into six groups. Each group attaches three of a different kind of index-card fin design to one of six paper-towel tube rockets:
- small fins near the front of the rocket
- small fins near the middle of the rocket
- small fins near the back of the rocket
- large fins near the front of the rocket
- large fins near the middle of the rocket
- large fins near the back of the rocket
Each group should be allowed some creativity with their fin design, within some basic size constraints: close to 0.5" poking out for small fins and close to 1.5" for large. Once the fins are attached, we adjourn outside for launch testing.
The way that fins stabilize the rocket's flight is actually very interesting, though if it seems like the class isn't getting it, we can simplify the learning goal to be that fins make the rocket's flight more stable without getting into why. The fins provide surface area for the wind to push against. When the rocket tips, the wind pushes harder against the extra exposed surface area so that the rocket rights itself. So in that sense the surface area of the fins is a little bit like the rocket's "support base". One difference is that you don't want the fins to be too big because then you get too much drag from air friction, and the rocket doesn't go as high.
The rocket pivots around its center of mass, so we want the fins to be behind the center of mass of the rocket for the most stable flight. So, I expect the large fins near the back of the rocket to give the most stable flight. But, there are many factors at play here, and given the crazy designs kids come up with, you may be surprised! The important thing is to get them thinking about what is going on with their individual rocket, and why it flies the way it does.
- Nasa: More in-depth rocket education material is available on NASA.gov. There is a Rocket Educator Guide (K-12).
- Rocket Stories for the younger grades:
- If You Decide To Go To The Moon, by Faith Mcnulty
- The Magic School Bus Takes a Moonwalk, JE 523.3 Cole
- Step Into Reading Rockets JE 919.904
- Blasting Off: Rockets Then and Now, by Steve Otfinoski (J 629.475)
- The Rooftop Rocket Party, by Roland Chambers
- Goldilocks and the Three Martians, by Stu Smith
- Astro Bunnies, by Christine Loomis
- This Rocket, by Paul Collicut
- Curious George and the Rocket
- Roaring Rockets: Amazing Machines, by Tony Mitton
- There's a 'step into reading' book called 'Moonwalk' about the first moonwalk.
After doing a selection of the above activities, get students' revised thoughts on air: what it is and what it can do. Maybe write these up on a board. The activity is not meant to take a lot of time, but if there is a little extra, it might be fun to have the students visualize air pressure pictorially. The technical definition of air pressure is force per unit area. An explanation that would make more sense (to the younger students) is that air is made up of lots of invisible little pieces that bounce around and hit things: people, walls, chairs, etc. Inside a bottle, the pieces are bouncing around and hitting the interior walls of the bottle (with, as we have seen, a non-negligible force). Have them draw a bottle (you might need to draw a bottle on the board for them to copy) and make representations of air hitting it. Notice whether anyone draws air pushing out from inside the bottle and in from outside the bottle (which is what is really going on).