Key concepts
Gravity
Weight
Lift
Aerodynamics

Introduction
Have you ever seen a helicopter flying through the air? Have you ever wondered how they fly—or if you could try flying one yourself? This fun activity will help you get started at home building a simple paper helicopter. And you will learn a little bit about what keeps these amazing vehicles aloft.

Background
Helicopters stay in the air using spinning blades that are used to generate "lift." With enough of it, a craft can overcome the force of gravity, which pulls the object down toward Earth. Aircraft such as helicopters with spinning blades are called rotary wing, unlike traditional airplanes, which are fixed wing.

In this activity you will build a simple paper helicopter called a "whirlybird." Unlike a real helicopter, the whirlybird does not have a motor to make its blades spin. Due to its special shape, however, the blades will still spin as it falls. This generates additional lift that slows the whirlybird even as it drops. So, it will fall much slower than if you crumpled up the same piece of paper and dropped it. Do you think adding paper clips as weights to the whirlybird will make it fall faster? Try this activity to find out!

Materials

• Computer with access to a printer to print the whirlybird template (If you do not have access to a printer, you can use a ruler and pencil to draw your own whirlybird template based on the online one.)
• Printer paper
• Scissors
• Several paper clips
• Stopwatch (optional)
• A safe, high place from which to drop the whirlybirds (You could have an adult stand on a chair or stepping stool, for example.)

Preparation

• Download and print the whirlybird template from this pdf. If you do not have access to a printer, you can download the file and open it on your computer, then use a pencil and ruler to draw the whirlybird shape on a piece of paper, based on the dimensions in the template.
• Follow the directions on the template to cut out and fold your whirlybird.

Procedure

• Now it's time to drop your whirlybird! What do you think will happen when it gets dropped? Have an adult help drop it from a safe high place (such as standing on a chair or a stepping stool). How did the whirlybird fall?
• Now drop the whirlybird a couple more times—in the same fashion, from the same height. Why do you think it is important to drop it more than once?
• Now, attach a paper clip to the bottom part of the whirlybird and drop it again. Do you think it will fall faster? Pay close attention. How did it fall with a paper clip attached?
• Keep adding paper clips, one at a time, to your whirlybird and drop it after each new paper clip. What do you observe as you add more and more paper clips?
• You can also use a stopwatch to time how long it takes the whirlybird to fall with different numbers of paper clips on it. Write down the times to help you remember how fast it falls when you add different numbers of paper clips. Do you detect a pattern?
• Extra: Try making whirlybirds from different types of paper, such as printer paper, construction paper and cardstock. Do the different types of paper fall at different speeds?
• Extra: Try modifying the whirlybird template or making your own design. For example, what happens if you make the "wings" longer or shorter or narrower or wider? What if you make the edges of the wings wavy or zigzagged instead of straight? What if you make the wings curved instead of rectangular? Try out a bunch of different ideas to see what happens. Then try to design your own whirlybird—one that falls as slowly as possible.

Observations and results
When you drop a whirlybird, it will take a fraction of a second for it to start spinning and slow down. This is why you need to drop it from a high location—it still needs a certain amount of vertical space to begin its spinning. Once the whirlybird does start spinning, it should "helicopter" slowly to the ground. As you add paper clips, the whirlybird should fall faster and faster until eventually it drops so fast that it does not spin at all.

Experimenting with your own whirlybird designs can be a fun and challenging engineering activity. There might not be one single design for the "best" whirlybird. Some designs might fall more slowly than others. If you change the dimensions too dramatically, however, a whirlybird may actually become unstable and tumble to the ground instead of spinning.

More to explore
Whirl-y-Bird versus Whale-y-Bird, from Science Buddies
How Do Helicopters Fly?, from Decoded Science
Soaring Science: Test Paper Planes with Different Drag, from Scientific American
Science Activities for All Ages!, from Science Buddies

This activity brought to you in partnership with Science Buddies