Freethought & Rationalism Archive

Mageth · 05-01-2003, 08:17 AM

The ball retains its original orientation. (Honestly, I worked this out "mentally" with two imaginary balls before reading tronvillain's excellent explanation.)

One thing I did that helped was doing away with the "fixed" qualifier of the first ball. Just don't let the two balls "spin" relative to each other.

Another mental image, related to the flat-surface or mirror examples, and an easy one to test. Picture a round bowl on a flat surface. Flip the bowl over and draw a circle around its circumference. Mark the circle's center and set the bowl on the center. Without "spinning" the bowl, rotate the bowl to "stand" on its edge on the drawn circle, roll it on its edge around the circle , and then rotate it back to its bottom on the center mark. The orientation of the bowl won't be changed.

Farren · 05-02-2003, 06:18 PM

The ball rotates along the Y axis by the amount it has rolled around the equator. The pole orientation remains the same. See attached image.

Jayjay · 05-02-2003, 06:25 PM

Your image is faulty. If you start with "the white dot" touching the fixed ball, and roll it to the equator, then point where the balls touch will have moved.

Jayjay · 05-02-2003, 06:38 PM

Picture.

Farren · 05-02-2003, 06:45 PM

Quote:

Originally posted by Jayjay
Your image is faulty. If you start with "the white dot" touching the fixed ball, and roll it to the equator, then point where the balls touch will have moved.

Oops! Aargh! and I deleted the source doc. Too tired to try again. oh well.

Actually from your subsequent illustration the answer's clear.

05-03-2003, 01:14 AM

Nice thread.

It seems no matter how the "rolling" ball is rolled, it will always come back to the same orientation. So it doesn't matter which ball is considered "fixed" or "rolling". If you "roll" with the "rolling" ball, the "rolling" ball is perceived to be "fixed" and the "fixed" ball becomes the "rolling" ball.

Everything is perception. I mean...perception is everything. Hmm.

Grand Ol Designer

Wyz_sub10 · 05-03-2003, 10:07 AM

I just want to say that moderating this thread makes my head hurt.

Jabu Khan · 05-07-2003, 06:25 AM

I don't know if this has been answered correctly or not yet . But i would say when you roll the ball to the equator and roll it back up those are opposite action so the ball comes back to the same position, When you roll it along the equator the axis of rotation is perpendicular to the previous one and so has no effect on the outcome.

johngalt · 05-07-2003, 04:27 PM

It would be hard to tell, and i don't feel like hurting my brain, so i think that the answer is------------no.

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05-01-2003, 08:17 AM	#71
Mageth Contributor Join Date: Jul 2001 Location: Deep in the heart of mother-lovin' Texas Posts: 29,689	The ball retains its original orientation. (Honestly, I worked this out "mentally" with two imaginary balls before reading tronvillain's excellent explanation.) One thing I did that helped was doing away with the "fixed" qualifier of the first ball. Just don't let the two balls "spin" relative to each other. Another mental image, related to the flat-surface or mirror examples, and an easy one to test. Picture a round bowl on a flat surface. Flip the bowl over and draw a circle around its circumference. Mark the circle's center and set the bowl on the center. Without "spinning" the bowl, rotate the bowl to "stand" on its edge on the drawn circle, roll it on its edge around the circle , and then rotate it back to its bottom on the center mark. The orientation of the bowl won't be changed.

05-02-2003, 06:18 PM	#72
Farren Veteran Member Join Date: Nov 2001 Location: South Africa Posts: 2,194	The ball rotates along the Y axis by the amount it has rolled around the equator. The pole orientation remains the same. See attached image.

05-02-2003, 06:25 PM	#73
Jayjay Veteran Member Join Date: Apr 2002 Location: Finland Posts: 6,261	Your image is faulty. If you start with "the white dot" touching the fixed ball, and roll it to the equator, then point where the balls touch will have moved.

05-02-2003, 06:38 PM	#74
Jayjay Veteran Member Join Date: Apr 2002 Location: Finland Posts: 6,261	Picture.

05-03-2003, 01:14 AM	#76
GrandDesigner Guest Posts: n/a	Nice thread. It seems no matter how the "rolling" ball is rolled, it will always come back to the same orientation. So it doesn't matter which ball is considered "fixed" or "rolling". If you "roll" with the "rolling" ball, the "rolling" ball is perceived to be "fixed" and the "fixed" ball becomes the "rolling" ball. Everything is perception. I mean...perception is everything. Hmm. Grand Ol Designer

05-03-2003, 10:07 AM	#77
Wyz_sub10 Veteran Member Join Date: Aug 2002 Location: In the land of two boys and no sleep. Posts: 9,890	I just want to say that moderating this thread makes my head hurt.

05-07-2003, 06:25 AM	#78
Jabu Khan Veteran Member Join Date: Apr 2003 Location: the impenetrable fortress of the bubbleheads Posts: 1,308	I don't know if this has been answered correctly or not yet . But i would say when you roll the ball to the equator and roll it back up those are opposite action so the ball comes back to the same position, When you roll it along the equator the axis of rotation is perpendicular to the previous one and so has no effect on the outcome.

05-07-2003, 04:27 PM	#79
johngalt Regular Member Join Date: Apr 2003 Location: Chicago, IL Posts: 204	It would be hard to tell, and i don't feel like hurting my brain, so i think that the answer is------------no.

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