There are those times when you get done early and have 10 minutes to kill before the next activity.  All you'll need to do is raid the scrap paper box and hand a pair sciossors to each kid.  Three cuts, five folds and you can make these cool helicopters in about 2 minutes (add 20 minutes if you teach kindergarten or first grade).  Not pickin' on anybody, i'm just sayin'…

Fourth grade science students in Hermosa Beach, California did this activity as part of a unit on flight.  The kids had a lot of fun and really enjoyed the activity.  One year I had a very social bunch and they loved to talk.  All of the time.  No matter what I did they would still visit with each other after just a brief moment of silence.

So we are engaged in this lab and I am, as usual, shooshing them. And they are a little more talkative than usual.  Actually, a lot more talkative and it is driving me nuts so I stop them in the middle of the lab and tell them that if they do not start experimenting quietly that I will hand them a monster home work assignment. There was a moment of quiet immediately followed by more yacking.

I  waited until the end of the lab period and as they were ready to go out the door I told them that their homework assignment, due when I saw them next week, was to take the original design and adapt it to create 50 new helicopters.  They could use different materials, add rotors, change the dimensions, whatever they could dream up was fine but the litmus test was that it had to spin to the ground when it was dropped.  And, as you would expect they stared at me for a second then started yacking again.
 

I forgot about the assignment until the following week when I was outside on bus duty.  I am unloading kids from the buses when fourth grade students start pulling up to the curb and getting out of their cars with these giant garbage bags full of something.  My vote was some project for social studies until one of the kids rolls up to me and announces, “That was the coolest homework assignment ever. I made 70 helicopters!”  It immediately occurred to me that I now had approximately 1500 helicopters to grade.  The kids came to lab that day, busting a jaw, as usual, but they were also really excited to show me all of the designs that they had created.

The thing that was really cool about this was that there is no way that I could have dreamt up half of the ideas that they presented.  But even more amazing was that as each kid showed off his top three designs all of the other kids were stone, cold quiet.  They were attentive, engaged, thoughtful, and it changed the way I presented science lessons forever.  Give them ownership, reward creativity, encourage originality and the kids will blow you away with what they produce.

The Activity:

1. Use the template on the edge of this  page as your guide when you are cutting your helicopter. 

2. Cut 1.75” off the bottom of a sheet of paper.  This will give you a long, skinny rectangle.  The next cut to make is along the dashed line that is between the letters A and B.  After that, make two small cuts directly above the letters C and D.

3. Once you’ve made your cuts,  fold one of the long strips (A) to the back,  crease it along the solid line, and fold the other strip (B) toward the front. These are the rotors of the helicopter-like samara and, at this point, it should look like a giant capital I with bunny ears.

4. Fold the sides (C & D) into the middle, just as you would fold a legal letter. This is the body of the helicopter.
   
5. The last thing to do is to fold the bottom (E) of the samara up about half an inch. This fold helps keep everything together.  A cartoon of what the final contraption should look like is pictured above.

6. Using the digital scale or triple beam balance, weigh your helicopter. Record the mass in kilograms on your Data sheet.

7.  Assume the helicopter flying position:  Stand on a chair, extend your arm with the helicopter in the air just barely touching the paper clip hanging from the ceiling, this is 2 meters above the floor.  Place your other hand on your hip.  Drop said invention from outstretched, overhead arm.  Make appropriate ooh-aah noises.  If the spirit of Sir Newton is with you, your helicopter will twirl to the floor.

Here's video with Mrs. Alexander's 6th grade class in Sandy, Utah

How Come, Huh?
This is a simple exercise in air friction which produces the unbalanced forces that you are studying.  As the helicopter falls to the floor, the air molecules push up against the “blades” and slow its descent.  The official  term for this resistance to the movement of the helicopter is called air friction or, sometimes, drag.  It spins  because the “blades” are on opposite sides, causing unbalanced forces that spin the helicopter. 

When you flip-flop the “rotors,” the forces are still there, but they are reversed, so the helicopter spins in the opposite direction.  If you start with the rotors pushed down there is resistance to the movement of the air over the rotors and it is so great that it actually disrupts the smooth falling of the helicopter and it tumbles to the ground.

Finally, as you shorten the “blades,” the surface area of the blades is reduced.  Less surface area means that there is less drag or friction pushing back up on the helicopter.  With less friction the helicopter falls toward the earth faster.  Additionally, there is less mass to push around and less friction resisting the fall, so the “rotors” spin faster.  This also translates into a faster descent to the ground, as you measured.