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9 May 2024 22:57
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| Asked by: |
Paul Kenyon |
| Subject: |
a moon's trajectory changed... |
| Question: |
Hi,
I have been pondering gyros (for a long time...my family makes gyro stabilizers for hand held optics so I've been around them since I was a baby...which doesn't mean I understand them any better it just means I've been in "wow!" mode for a very long time) and have the following thought experiment to offer. I'm wondering about its validity...so that is the question.
I imagined a moon circling a planet (like ours) The moon is small. It's been said (and I agree) that anything that rotates as gyroscopic properties...such as celestial bodies, moons, spinning planets, galaxies...)Approaching the moon I see that the trajectory appears a straight line. I see a force hit the moon normal (at right angles) to the moon's trajectory and, naturally, it deflects it. The moon gains a little energy in this exchange, of course, and is moving faster as it continues around the planet. At the bottom of it's trajectory (I've raced around to view it again) it is hit by another force of the same magnitude as the first force but in the opposite direction. The moon is deflected again and again gains energy. Back on top the moon comes by and it is in the same location as it was when the first force hit it but its trajectory has rotated (and it's moving faster as a vector analysis of the two collision-like events would show.) What I see here is a strong argument for the small element deflected explanation (the one scoffed at in the video #18 of the '74-5 Christmas Royal Academy lecture) of gyroscopic motion. I note the precession but also the additional energy of the element.
Reviewing this (my thinking, that is) I see that I have not worked out whether or not the deflection of the ring (moon's trajectory) follows the rules that predict the direction of precession given the sense of spin and direction of input force that causes precession...but I think it does.
A note here...one of my thought experiments was to take a spinning gyro, stop it and spin the forces instead. The example or situation I used was the common one wherein you put the spinning gyro axel end on a support, axel horizontal, and see that it does not fall over but precesses instead. If you spin the forces instead of the gyro in an analygous way you get to appreciate (if nothing else is gained from this) the complexity of the forces put on the wheel (just try to draw them. The experiment is easy and done by every boy and girl playing with a bicycle wheel removed from the bicycle and held by the quick release. I noticed the forces and replicated them in my above thought experiment...though, for the experiment, they are much simplified...reduced to only a couple.
Yesterday I received delivery of a "Powerball" by Dynaflex. It is billed and sold as a device to strengthen forearms, etc. It's a gyro. You get it going and add energy to it by manipulating it while holding it in your hand. It's about the size of a tennis ball. Well, it works. Apparently you can get it up to about 13,000 rpm. At much fewer rpm's than that it has considerable gyroscopic aspect. Everyone interested in gyros should own one of these. It's about $US16.00 + shipping. The literature says it's not a toy but a precision device. I'll attest to that. It takes a knack to get it going but you'll get the hang of it. I did...and I'm a klutz. |
| Date: |
5 January 2007
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