# Gyroscopes

 Physics, Engineering: Angular Momentum Grade Range: Elementary School, Middle School, High School Format: Hands-on

Gyroscopes are seemingly mystifying, and they can keep curious students occupied for a while.

## Materials

• Gyroscopes with Stands
• String

## Safety Precautions

Please read the General Safety section of the Demonstration Safety page before performing this demonstration.

## Demonstration

1. Set out the gyroscopes, the stands, and the lengths of string on a table. While waiting for students to come by, wind up one or two of the gyroscopes with their strings, being sure to first have it go through the hole in the bar before winding.
2. As students come by, show them the gyroscopes and ask them to try and get them to stand upright. Allow students to make attempts until they either figure it out or give up before showing them how to wind the gyroscope.
3. After explaining how they work, have students try to make a gyroscope stay on a stand, or balance on their finger! For older students, have them attempt to make the gyroscope stand on a string!

## Why This Works

Gyroscopes are spinning wheels or discs that are inside of one or more frames, and while spinning they can orient themselves regardless of the orientation of the outer frame(s). This is possible because of the high angular momentum that a gyroscope has while spinning. Angular Momentum is when the momentum of something is around an axis, rather than being on a straight line. The amount of momentum that something has is dependent on two things: velocity, or how fast it is moving, and mass or how big the object is. With our gyroscopes, the center wheel has a lot more mass than the outer frame. When we spin the wheel, it then has a velocity. Our wheel now has momentum, and because it is spinning on an axis it has angular momentum.

Momentum has to always be conserved, which means that it cannot suddenly disappear or magically appear. This also means that when something has momentum, it will continue to travel that way and push against things that will try to change it. Our gyroscope behaves like a top, and both do so because of the conservation of angular momentum. While spinning upright, it does feel the tug of gravity downward that wants to make it fall over. But because it has a lot of momentum, the momentum will keep it upright so that it can stay on the same spinning axis. This is also why the gyroscope will stay on a stand or on your finger, even when it is spinning sideways! Because the angular momentum has to be conserved, the gyroscope will continue to spin in the same direction, regardless of what direction gravity pulls on it!