Tops - for time & speed
I have long been a fan of Newton disks, which show when the colors of the spectrum, in the right proportion and speed will blend together and appear white. With an optical tachometer that I bought for less than $20 on eBay I found that the commercial disk needed to spin at about 3200 RPM to see the white effect. I wondered if we could make a top that would spin fast enough to produce the white effect.
Using a whole cutter and heavy cardboard I made many, many disks for our tests. Fortunately, pencils are a good fit for the hole make by the whole cutter and if needed you can use tape to make the pencil slightly larger.
Materials need Tools
heavy cardboard Drill motor
pencils Hole cutter
tape Stop watch - on cell phones
pennies Optical tachometer - optional
aluminum foil, shinny metalic tape or ribbon Hot glue gun - optional
Using a whole cutter and heavy cardboard I made many, many disks for our tests. Fortunately, pencils are a good fit for the hole make by the whole cutter and if needed you can use tape to make the pencil slightly larger.
Materials need Tools
heavy cardboard Drill motor
pencils Hole cutter
tape Stop watch - on cell phones
pennies Optical tachometer - optional
aluminum foil, shinny metalic tape or ribbon Hot glue gun - optional
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Variations:
Size of disks
number of disks
pencil size: length, short golf pencils
Spinning point: sharpened point or eraser end. This had some some surprising results.
Pennies for weight
Arrangements of weights towards the edge. Pennies can be taped to the outer edge.
Teaching/Investigation tips
I set up some preliminary investigations to help
Place the disk high and low on the pencil (center of gravity)
Place penny weighs close to the axis and near the edge
Size of disks
number of disks
pencil size: length, short golf pencils
Spinning point: sharpened point or eraser end. This had some some surprising results.
Pennies for weight
Arrangements of weights towards the edge. Pennies can be taped to the outer edge.
Teaching/Investigation tips
I set up some preliminary investigations to help
Place the disk high and low on the pencil (center of gravity)
Place penny weighs close to the axis and near the edge
col
Image sources:
- Newton's Disk http://www.daviddarling.info/encyclopedia/N/Newtons_color_disk.html
- Optical Tachometer: generic picture from simplemotor.com
- Hole saws: harbor freight
- Newton Wheel in color- www.fizzicseducation.com.a
- Newton Disk pattern: http://etc.usf.edu/clipart/20100/20109/newtondisk_20109.htm
Image sources:
- Newton's Disk http://www.daviddarling.info/encyclopedia/N/Newtons_color_disk.html
- Optical Tachometer: generic picture from simplemotor.com
- Hole saws: harbor freight
- Newton Wheel in color- www.fizzicseducation.com.a
- Newton Disk pattern: http://etc.usf.edu/clipart/20100/20109/newtondisk_20109.htm