Turntable

At the “Turntable” exhibit, you’ll see a disk that rotates like a giant compact disc. Use the supply of small plastic disks, rings, and balls scattered around the table top. Try to keep the rings on their edges spinning on the disk. You may get a ring spinning on its edge to stay on the turntable for a while, orbiting the center. A disk laid flat on its side will move in a straight line as soon as it slides off the turntable. Try your skill at getting the disks and rings to stand on edge while moving around the disk.

You’ll notice a disk on the “Turntable” exhibit moves faster near the outer edges than it does at the center, just like a CD player. To adjust for this, a CD player is constantly changing the speed at which it’s spinning — it spins faster when playing tracks near the center of the disk, and slower when playing tracks near the outside.

A CD has a single spiral track of data, circling from the inside of the disc to the outside. The data track is incredibly thin ­— approximately 0.5 microns wide, with 1.6 microns separating one track from the next. (A micron is a millionth of a meter.) The spiral track on a CD, however, is extremely long. If you could lift the data track off a CD and stretch it out into a straight line, it would be 0.5 microns wide and almost 3.5 miles long!

Questions to Ask

Why do the standing rings stay on the disk?

Describe their motion compared to the spinning surface?

Does the direction of the small disk’s spin control the direction of the slide the small disk takes?

What happens to a ball when placed near the center of the spinning disk?

How is this turntable like a merry-go-round in the playground? What happens when you try to walk around on the merry-go-round?

Relevant Arkansas Science Frameworks

(PS.6.1.1), PS.6.2.1, PS.6.4.1, PS.6.7.6, P.6.PS.11, P.6.PS.6, P.6.PS.11

"Mini-Vibe" — An activity to do at home or in the classroom