CreatZy Physics Notes

PowerBall Gyro is simply a gyroscope with the size of an apple, but it can bear a real monster of spinning energy! When spun up to about 5000rpm, it needs a stack of books about 6kg loaded upon to be "controlled". (I've recorded that scene, but have no host :( to upload)

"The more you KEEP it, the more it REACTs!
The only way to stop it is to LET IT FREE."

This fact is not only philosophical any more, but physical! As long as you hold the PowerBall Gyro tight, your hand acts a force on the spinner inside and causes its precession, as a result, it reacts onto your hand. Want it to stop turning crazily (its precession and nutation)? Just release it: loosen your hand, put it on a table, or even hang it up!

More than force, when you try to "control" the PowerBall Gyro by holding it tight, you have given it energy.
To prove this, I have done an experiment about the decelerating time of PowerBall Gyro from its 4Krpm spinning until it stops.

Experiment repeation: 5 times

• Held case: the PowerBall Gyro is held tightly down to table.
  Recorded average time: 4K-3K: 15s; 3K-2K: 30.6s; 2K-1K: 28.4s; 1k-0: 3.2s; 4k-0: 77.2s


• Released case: the PowerBall Gyro is released to stand freely on table.
  Recorded average time: 4K-3K: 7.8s; 3K-2K: 9s; 2K-1K: 10.6s; 1k-0: 8.4s; 4k-0: 35.8s

You can see that the spinning time in "held case" is lengthened up to double the time of that in "released case".

Futher more, you can see the spinning time of each range of speed is different from each other in "held case", while almost uniform in "released case". Thus, we can infer that in "released case", the deceleration is only due to friction; while in "held case", the holding force has given energy for it to continue spinning against friction.


However, there is still an open question for me is that, "How can the force on the outer shell cause acceleration of the inner spinner?"

-------------------------------
Jan 20th 2007 (Supplement)

Hey, thanks to YouTube, I have uploaded the webcam-recorded video:



Because being shot with the pc webcam, it's not so clear. But you can see the whole stack of books swinging for a few seconds at first, and the inner rotor spinning clockwise when it stops at the last second.

↑top↑ ↑archives↑