Physics and a Gyroscope Toy

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This post explores one of the cores of toys and physics. A gyroscope. We are going to learn a lot about this simple yet amazing device. You may have seen it before, but I’m sure you did not know all the fantastic things this device can do… like defying gravity…
Gyroscope Animation 

What is a Gyroscope?

Anything that spins could be a gyroscope. Be it a top, a disc, a bicycle wheel, a space ship, and even a planet or a star.
 
In its most practical and know form, a gyroscope is a spinning disc that rotates over an axis through its center. It is free to take any orientation by itself. When gyroscopes rotate, they can do amazing things that seem to defy gravity.
 
These are mind-boggling and very non-intuitive devices. They behave in strange ways. But this strange behaviour gives place to some of the wonders of the modern world.
 
Space shuttles would not be possible as we know them without gyroscopes.
 
Travelling as it is today would be impossible without the help of gyroscopes.
 
This is why gyroscopes are at the core of toys and physics. If there is one device that pictures everything this site represents, that is a gyroscope.
 

What does Gyroscope Mean?

As most things in science, this word comes from the ancient Greek, γῦρος gûros, “circle” and σκοπέω skopéō, “to look”.
 
In other words, and I may be interpreting a bit, a gyroscope is something that allows you to see rotation.
 
According to history, many devices like gyroscopes were present in ancient civilizations.
 
But it was until 1852 when, Léon Foucault (yes, the pendulum guy), used it to show Earth’s rotation. Léon Foucault named this device, gyroscope, which is the name we used until today.
 

How does a gyroscope work?

Everything has to do with the rotating disc. If you have a gyroscope and the disc is not rotating, there is nothing special about it. The gyroscope behaves like any other object.
 
But when the disc is rotating, everything changes. This rotational motion makes the gyroscope behave in strange ways.
 
Rotation helps the gyroscope defy gravity and move in ways we may not expect.

 

What is the Gyroscopic Effect?

Football Perfect Spiral
When Tom Brady throws the ball to hit that touchdown, it is very important that the ball is easy to catch. To help the receiver catch the ball, Tom must ensure the ball spins describing a perfect spiral.
 
The better that spiral is the more stable the ball will travel. This will help the ball as well travel a longer distance. At the same time, this will make it easier for the receiver to catch the ball.
 
What we have to look at here is that spiral. The spiral will only be good if the the ball is not wobbly.
 
If the ball wobbles a bit, the ball may not reach the receiver with the precision needed.
 
But if the ball describes a perfect spiral, then it is not only easier to catch, but the pass is more precise as well.
 
When the ball is spinning in a perfect spiral, it also acts like a gyroscope. The precision we are talking about, is due to something called: rigidity in space.
 
This is the gyroscopic effect. A “force” that helps spinning masses to keep a specific orientation, even if “other forces” act upon them.
 
In our example, the spinning mass is the football travelling from Tom to the receiver. The other forces are air resistance and even rain or snow falling from the sky. This gyroscopic effect helps the ball travel, with precision, regardless of other forces.
 
Of course these other forces are small and this is why gyroscopic effect seems unaltered. If the other forces are strong enough, the football will deviate from its trajectory.
 
The same is true for a coin. Place a stationary coin on its side and it will fall. But roll it over a surface and the coin will continue to move for a while.
 
Why?
 
Thanks to the gyroscope effect of rigidity in space.
 
Immediately, lots of examples are available. A top spinning, a bicycle, a motor cycle, and… lots of electronics which you may not know have gyroscopes inside.
 

What is Precession?

Wobbly Football
There is another effect of gyroscopes that you must know about. Precession.
 
Spinning objects display precession. We call precession to the change in orientation of the axis on which the gyroscope spins.
 
To put it simpler…
 
In his last pass, Tom threw the football and this was spinning in a perfect spiral. It was rotating on its longest axis, and the pass was nice and smooth.
 
But…
 
Now imagine Tom throws a very long and high pass. Due to the length and altitude of this pass, the ball lost most of that spiral when travelling. Now, gravity is exerting a lot of effect on it.
 
This makes the football wobble a bit.
 
This wobbling is precession.
 
In a nutshell, precession is the change in the orientation of the spinning axis of a rotating mass.
 
In this case, the football rotation axis is no longer pointing forward, because it wobbles. Instead, the football rotational axis describes a cone-shape.
 
Precession is another gyroscope effect that rotating masses display.
 
Take a football and spin it on the floor. At first, the ball may spin niche and smooth, but after a while the ball will start to wobble.
 
Same is true for a top spinning, and any other rotating object. Unless you attach a motor or something to keep its spin, the rotating object will show precession.
 
And…
 
Even with motors, small changes in speed can lead to precession of a rotating object.
Precession Gyroscope 

A bit about physics of toy gyroscopes

There are a bunch of physics concepts that gyroscopes can teach. But the ones I’d like to mention are moment of inertia and angular momentum.
 

What is moment of Inertia?

Gyroscope Moment of Inertia
The moment of inertia tells us how difficult would be to spin an object. Also, it can tell how hard would be to stop a spinning object.
 
You can think of the moment of inertia as the rotational mass of the disc. Note that different mass arrangements will produce different moments of inertia.
 
Picture a merry-go-round, with children close to the center (axis) of rotation.
 
Now…
 
The same merry-go-round, with the same children, but, at the outer edge of the merry-go-round.
 
Question!
 
Which one is easier to spin?
 
The first one, right? Well… that is because of the moment of inertia of each configuration.
 
In both cases, we have the same amount of kids. The same merry-go-round. So the mass is the same in both cases.
 
Yet, you’ll need more force in the 2nd case to start or stop the merry-go-round.
 
Again, the moment of inertia is higher when the children are at the outer edge of the merry-go-round.
 
As you can imagine, the moment of inertia depends on the mass of the objects.
 

What is angular momentum?

Gyroscope Angular Momentum
So far we’ve been saying that gyroscopes seem to defy gravity thanks to a “force”.
 
Well…
 
This “force” is not a force, it is in fact, angular momentum.
 
Angular momentum is what keeps the top spinning once you get it started.
 
In physics, they say angular momentum is a conserved quantity. This means that if no other forces act upon a spinning object, the spinning object will spin forever.
 
Why tops and gyroscopes don’t spin forever?
 
Well…
 
You have gravity acting over the top. Also, there is air resistance, friction between the top and the table it spins over.
 
These act upon the top and thus the top stops spinning.
 
But…
 
While it spins, its angular momentum keeps it spinning and this is why it is as if a top or a gyroscope defies gravity.
 
It is even more impressive when you see a gyroscope spinning not on top of a table, but almost hanging from a string.
 
The coolest thing is the gyroscope points upwards instead of downwards or to a side. That is so impressive.
 
Something else I want to mention about the angular momentum, is it is a vector. This means that besides being a number, it also points somewhere.
 
The direction of angular momentum explains why gyroscopes don’t fall when spinning.
 
Angular momentum is always perpendicular to the direction of rotation.
 
The right hand side rule is a simple and powerful way to know the direction of angular momentum.
 
With your right hand, twist your index, middle, anular, and pinky fingers in the direction of the spin. Now keep your thumb straight up or down depending on the direction of rotation.
 
Thus, your thumb will point in the direction of angular momentum.
 
Be it up or down, if the angular momentum has a vertical orientation, the gyroscope won’t fall.
 
This is because angular momentum conserves itself until external forces end it.
 

What is a gyroscope used for?

Gyroscopes have many applications in the modern world. In a nutshell, anything that needs to know its orientation, can use a gyroscope.
 
This is the main use of a gyroscope: provide with orientation.
 
Let’s think of this for a minute. The main characteristic of a gyroscope, is the conservation of its angular moment.
 
So, if the gyroscope could spin forever, it would point in the same direction no matter what.
 
If you were to travel through space, where is hard to tell left from right and up from down, a gyroscope would be useful. You could set it in a direction and travel on a straight line.
 
Well…
 
You don’t have to go to space to see the benefits of a gyroscope. Ships use gyroscopes and instruments that evolved from gyroscopes to navigate the seas.
 
Planes use gyroscopes to detect their orientation and thus keep everything horizontal.
 
Even you phone has a gyroscope to know when your device turns 90 degrees and thus adjust the screen size and ratio.
 
The same is true for any screen that responds to changes in orientation.
 
If you think about these self-balancing gadgets, can you tell me the basis of this technology?
 
If you said: Gyroscopes, you got it right.
 
When you think about what gyroscopes do, you realize these do two things:
  1. Keep the orientation of its spinning axis.
  2. Tell the main computer of gadgets when there is a change in their orientation, to adjust as needed.

can a gyroscope produce electricity?

The short answer is yes. Electricity can come from any object in motion. In essence, every spinning motor generating electricity, is a gyroscope.
 
So yes, gyroscopes can help produce electricity.
 
The real challenge is to create electricity from a gyroscope on its own.
 
There are lot of proposals to generate electricity using gyroscopes alone. Some models seem promising, but the problem comes when we talk about efficiency.
 
This means the amount of power created is not enough to consider a gyroscope a source of electricity.
 
Some of the most acceptable models theorize a gyroscope made of permanent magnets. Wires forming a coil on the frame and connected to the magnets would create a magnetic field.
 
The interactions of these magnetic fields would create an alternating electric current.
 
In a nutshell, gyroscopes can create electricity, but efficiency may be a problem.
 

Do gyroscopes work in space?

Yes!
 
Gyroscopes are the basis of many navigational systems used by space vessels.
 
Without gyroscopes, navigation in space would not be possible. Everything from satellites, to telescopes, and shuttles use gyroscopes.
 

Closing thoughts about Gyroscopes

Gyroscopes are amazing devices that can teach a lot about physics. I bet gyroscopes will form the base of new technologies, as we learn more about them.
 
Also, science fiction movies base most of their spaceships designs in gyroscopic-type vessels.
 
And…
 
Gyroscopes already do a lot more for the modern world. By combining electronics and other interesting physics, other gadgets are possible.
 
Like I said, rotate your phone and you’ll see the screen adjusting thanks to one of these gyros.
 
That is all for now. Get a gyroscope and experiment a bit. Build your own and have fun doing it.
 
Till the next one!