Role of Angular Momentum in Frisbee

If you just apply a thrust force to a disc, it will go some distance, but not that far. However, if you apply more spin to the disc, the spin will stabilize the Frisbee, allowing it to go much farther. So how does spinning to this? Also in this blog, I will add on to my knowledge of the aerodynamic forces and its roles in angular momentum.

When a disc doesn’t spin, the aerodynamic forces are not on the center. What this means is that lift on one side of the Frisbee will be larger than the other side, creating a net torque. Torque is “a measure of how much a force acting on an object causes that object to rotate”. Once this torque is created, a stable flight is no longer possible as one side of the disc is popped up.


In this image, you can see that the center of mass is not where the center of pressure is. This will cause a torque.

Spinning gives an object angular momentum. This type of momentum is dependent on “Moment of Inertia”, I, and angular velocity, w. Therefore, L=I*W. The higher the angular momentum, the more stable the object will be.

What is moment of inertia? It is the inertia for a rotation. The moment of inertia depends on how far away mass is from the rotational axis. In other words, it depends on the distribution of mass. Also, it is the amount of resistance a body has to changing its state of rotational motion. The equation for I is MR^2. This equation is only for a solid cylinder or disc as other objects such as rods or shells will have different ones.

The faster the spin is, the more angular velocity there will be. If there is no spin, there will be no angular momentum as W=O. For example, with a motorcycle, the bike doesn’t stay upright because of the good balance of the motorist, it is from the high angular velocity from the wheels.

Since angular velocity talks about a direction as well, one can use the right hand rule to find it. Check out the next blog post to learn more about this.

Sources I used:

Role of Angular Momentum in Frisbee

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