Physics of Frisbee

When playing ultimate frisbee, you learn many different ways to throw a disk. The two most common methods of throwing are backhand and forehand throws. We will not dive into the physics of lift and the aerodynamics of a frisbee, rather, I will discuss the magnus effect on the disk and how it affects the trajectory and techniques for throwing. In order to keep this simple, we will only discuss the throws from a right handed perspective.

The motion of the disk from each of the two throws are mirrored. A backhand throw has the disk spinning clockwise while forehand throws spin counter clockwise when looking from the top of the disk. This means that a backhand throw has a tendency to curve towards the right while forehands tend to curve to the left. As you can see in the picture below, a ball or disk has a tendency to move towards the direction it is spinning. Note: the frisbee is traveling towards the right.

If a disk was thrown flat with a backhand spin into a big valley, the disk (from the thrower's perspective) will tilt clockwise until it is perpendicular to the ground and hits the ground. As the disk begins to tilt, it flies towards the ground because the clockwise spin from the tilted disk pushes it down. As the disk tilts during its flight, it will also fall faster because the spin is directed more and more towards the ground until the disk is perpendicular, during its flight. In order for a player to throw a frisbee far, we have to account for the Magnus effect. Players overcompensate by releasing the disk at an opposite tilt as where the disk wants to tilt. Therefore, a backhand throw will be release at a slightly more counterclockwise tilt, rather than flat. This technique makes frisbee go further because it keeps the disk relatively flat for longer, letting it float longer.

Now with all that you've learned about frisbee flights, which of the three throws with equal force and spin will fly the furthest?