Introduction

Are you good at tossing a Frisbee? Have you ever wondered how a Frisbee is able to fly through the air so well? If you can throw a perfect, arcing curve, right on target, you have already trained your arm on the aerodynamics of Frisbee flight! In this science activity, you will investigate how the angle at which you throw the Frisbee affects its flight’s direction and distance. Next time you are out tossing a Frisbee, this little lesson in aerodynamics may help make your throws be even better!

Time: 20-30 minutes

Key concepts: aerodynamics, forces, physics, lift, drag

Materials

• A Frisbee
• Long string or hose
• Tape measure
• Large open area to toss a Frisbee in
• Optional: A helper
• Optional: A piece of paper and a pen or pencil

Prep Work

1. Use the long string or hose to make a long, straight line in front of you, at least 25 feet long. You will be throwing the Frisbee so that it is directed down this centerline.
2. Practice throwing the Frisbee down the straight line a few times so you get used to tossing it. If you have not thrown a Frisbee much before, you may want to try practicing it for a little while. Tip: A good way to throw a Frisbee is by standing sideways with the Frisbee held in front of you (near the shoulder you are looking away from), then bringing the Frisbee horizontally across you as you throw it.
3. If there is wind during any of your Frisbee throws, note the wind speed and direction.

Procedure

1. Throw the Frisbee as flat and horizontal as you can, aiming it down the centerline you made. You can have a helper watch to confirm the angle at which you throw the Frisbee. Question: How far did the Frisbee travel? How far did it travel away from the centerline, and in what direction?
2. If you have a piece of paper and a pencil or pen, you can record this data and all following flight data.
3. Throw the Frisbee as flat and horizontal as you can at least four more times. Each time throw the Frisbee with similar arm motion and speed, use a similar spin, and have the same release point. How far did the Frisbee travel each time? How far did it travel away from the centerline, and in what direction?
4. Throw the Frisbee tilted up, aiming for between 1 o’clock and 2 o’clock (about a 45-degree angle up from the ground). Throw it this way at least five times. Other than changing the launch angle, try to keep all other aspects of the Frisbee flights the same. How far did the Frisbee travel each time when thrown at an upward angle? How far did it travel away from the centerline, and in what direction?
5. Throw the Frisbee tilted down, aiming for between 4 o’clock and 5 o’clock (about a 45-degree angle down towards the ground), at least five times. Again try to keep all other aspects of the Frisbee flights the same. How far did the Frisbee travel each time when thrown at a downward angle? How far did it travel away from the centerline, and in what direction?
6. Did you see a consistent relationship between launch angle and flight direction? Question: Is there a relationship between launch angle and distance? Why do you think you saw the relationships that you did?

What Happened?

To fly well, the Frisbee needs enough lift — which is the force that allows a Frisbee to stay in the air, and opposes the downward force of gravity — and not too much drag — which is the backward force on a Frisbee, going against its movement through the air. When a Frisbee is thrown tilted downward, it hits the ground sooner, so it does not have as much time to travel before it lands. As a result, it does not go as far. A Frisbee will go farther if you throw it horizontally or at an upward angle, since it will have a good amount of lift and will not crash into the ground right away. However, you may have noticed that if you throw a Frisbee up at too steep of an angle, it will probably stall out near the end of its flight, causing it to land gently and/or off to the side. When something flying through the air stalls, there is too much drag and not enough lift. Overall, the horizontal launches probably resulted in the overall “best” Frisbee throws in terms of distance and straightness.

Digging Deeper

Two key forces that act on a Frisbee during its flight are lift and drag. Lift is the force that allows the Frisbee to stay in the air, and it opposes the force of gravity on the mass of the Frisbee in flight. The Frisbee itself creates this lift force as it flies through the air. The Frisbee pushes air out of the way as it moves, and causes a slight downward motion of the air. The air pushes back up on the Frisbee, creating the lift force. Drag is a backward force on the Frisbee, and it goes against the Frisbee’s movement through the air, slowing it down. The force of drag acts perpendicular to the force of lift. The Frisbee’s shape, velocity, and angle at which it moves relative to the still air (called the “angle of attack”) all affect both the lift and drag.

As a side note, you have probably noticed that a Frisbee does not travel far if it is thrown without spin. Spinning the Frisbee helps it fly by supplying angular momentum, which helps keep the Frisbee stable while it is rotating. The faster it spins, the more stable it should be.

For Further Exploration

• In this activity, you investigated how the launch angle of the Frisbee affects its flight’s distance and direction, but you only tested a few angles. You can try this activity again but test even more angles, such as angles in between the ones you tried in this activity. You can videotape your throws and then watch the video to analyze and confirm the angles at which you threw the Frisbee. How well does the Frisbee fly using other launch angles? Is there an angle that consistently correlates with the “best” flight in terms of distance and stability?
• In this activity there was not a focus on the effects of wind on a Frisbee’s trajectory, but wind can definitely be a factor. How will the flight of the Frisbee be affected by throwing the Frisbee into the wind? What about across the wind or with the wind? How does the launch angle change the flight in each of these conditions?
• You could compare the flight of a Frisbee to the flight of an Aerobie (open ring flying disk). What differences do you notice? Can you explain them in terms of aerodynamic forces?
• The National Aeronautics and Space Administration (NASA) website has a great section on Aerodynamics. See The Beginner’s Guide to Aerodynamics.

Science Careers

Credit

Teisha Rowland, PhD, Science Buddies

Ben Finio, PhD, Science Buddies