Lift:

When a frisbee is thrown at what is called a positive angle of attack, with the nose pointing up, the air flowing over the top of the frisbee flows faster than the air flowing underneath. Why? The air on top has farther to travel, so it moves faster. This creates lift on the frisbee.

This is the same as what happens to an airplane wing because of how it's shaped. We have all experienced this lift when travelling in a car with our arm out the window. If we tilt our hand up while travelling along, we can feel our hand rising up. Like a wing, our hand is experiencing the force of lift.

It is lift that makes throwing a frisbee different from throwing a ball. Once a ball has left your hand, gravity is the only force acting on it. The force of gravity quickly pulls the ball down. A frisbee, on the other hand, actually flies because, as well as gravity pulling it down, there is lift pushing it up.

Angular Momentum:

Does this mean that if you take a frisbee, point its nose up, and push it away it will fly? No! If you try this, you will see that your frisbee will not go very far. It will flip up due to the air resistance. This is where the spin and angular momentum come in.

It is easier to understand angular, or spinning, momentum if you first understand linear momentum, for objects moving in a straight line. Linear momentum is the product of the mass of an object and its speed. This means that the heavier an object is, or the faster it is moving, the more momentum it has. If something has a lot of linear momentum it's hard to stop. It's a lot easier to stop a truck going at 1 km/h or a fly at 50 km/h than a truck at 50 km/h. It takes a lot of force to stop that fast moving truck.

Just as an object moving in a straight line has linear momentum, an object moving in a circle has angular momentum. The faster an object is moving in a straight line, the bigger the force needed to disrupt it. In the same way, the more spin an object has, the more torque or twist is needed to disrupt it. You can see the effects of angular momentum on a frisbee. The more spin a frisbee has, the harder it is to wobble it. Another example of this is a bicycle. It's very hard to sit on a bicycle that's not moving without falling over! It is a lot easier when the bike is moving because the wheels are spinning. Since they have angular momentum, it is harder to twist the bicycle to the ground.

• a light cloth (a J-cloth or cheese cloth will do)
• plasticine
• plastic wrap
• needle and thread

1. Cut a uniform circle out of the cloth. Make the circle a little bigger than the size you want your frisbee to be.
2. Take some plasticine and roll it into a long "snake". This snake should be a little smaller than the size of the perimeter of your cloth circle and not too thin. (Use a good helping of plasticine!)
3. Wrap your snake in plastic wrap to make it a little more durable.
4. Form your snake into a circle and place it near the edge of the cloth.
5. Overlap the edge of the cloth over your snake-circle and sew the flap down. You now have an amazing "Floppy Flyer Frisbee".

To investigate how your Floppy Flyer Frisbee flies:

1. Try throwing your Floppy Flyer Frisbee at different angles. Which direction produces the most lift?
2. Try experimenting with different sizes of Floppy Flyer Frisbees. Why do you think the size of the frisbee changes how it flies?
3. Try using different materials for the Floppy Flyer Frisbee. Why was it best to start out with a light cloth?
4. Try using different amounts of plasticine. What is the best amount to use?
5. Can you think of other experiments to do with your frisbee?

You can learn more about flight here.