# SPINNING DISKS

A disk on a string. When you pull on the twisted string, you put in WORK or ENERGY and as a result the disk will spin in one direction and then in the other direction. Once you get it started it will spin very fast and…as long as you put energy in it will keep going!

When discs or wheels, like a bicycle wheel, spin fast they ROTATE around their CENTER OF GRAVITY and they get a “mind of their own”.That is why you can stay on the bike, and why the whirling twirler works its magic!” When you hold a spinning bicycle wheel in your hands it is very difficult to change its position, it wants to stay where it is at that moment… This is called the gyroscopic effect, a bit difficult to explain, maybe at high school or college?

What in the world is a centre of gravity.

It is the point about which the disc will BALANCE. Put a ball on the floor and put a dinner plate on top, you can balance the plate if you put its center of gravity precisely on top of the ball. When it balances you have found the center of gravity of the plate, it is precisely at  the middle of the plate.  For other, not circular parts it might be in an other place on its body. Give it a try.

Here is a toy gyroscope, the rotor is spun at high-speed by a string and while it spins you can move the frame and the rotor stays perfectly in its plane of motion. Gyroscopes are used in aircraft, and u-boats and other things that need to stay on course. Modern compasses also use the gyroscope.

The TOP we have listed as a project is something you might try to make, it is a great toy and shows the gyroscopic effect beautifully.

The spinning disk is a spinning top on a string. It acts like a GYROSCOPE as it spins on its own around its center of gravity while the flexible string allows it to do that , AND… the string puts in the energy needed to keep the disks spinning. Well….this is getting difficult, but read on!

Open up an old hard drive of a computer and you find a spinning disk inside, great fun to take a drive apart and discover all kinds of nice things.

And finally these children are hanging on for dear life on this playground spinning disk…