Toffo Posted September 29, 2013 Share Posted September 29, 2013 Spin is relative just like velocity is relative What is your opinion about sawing? Sawing a log into two parts with a hand saw. Is sawing something else in some reference frames? If I think that I'm sawing, do people in some other frame think that I'm knitting? Link to comment Share on other sites More sharing options...
Endercreeper01 Posted September 29, 2013 Author Share Posted September 29, 2013 What is your opinion about sawing? Sawing a log into two parts with a hand saw. Is sawing something else in some reference frames? If I think that I'm sawing, do people in some other frame think that I'm knitting? No, but other people would see the saw's velocity change depending on what reference frame they are in Link to comment Share on other sites More sharing options...
Toffo Posted September 30, 2013 Share Posted September 30, 2013 (edited) No, but other people would see the saw's velocity change depending on what reference frame they are in Ok I agree. Let's now go back to the spinning hoop. A non-spinning hoop at rest: O A non-spinning hoop that is moving to the right very fast: | A spinning hoop at rest: o A spinning hoop moving to the right very fast: a "|" as tall as a "o" is the correct picture here, I would guess. When a loop is spinned up, it shrinks. When the spinning loop is accelerated sideways, it shrinks sideways. Right? I propose a law: When speed change is caused by time dilation, then there is no contraction related to said speed change. Edited September 30, 2013 by Toffo Link to comment Share on other sites More sharing options...
Endercreeper01 Posted September 30, 2013 Author Share Posted September 30, 2013 Ok I agree. Let's now go back to the spinning hoop. A non-spinning hoop at rest: O A non-spinning hoop that is moving to the right very fast: | A spinning hoop at rest: o A spinning hoop moving to the right very fast: a "|" as tall as a "o" is the correct picture here, I would guess. When a loop is spinned up, it shrinks. When the spinning loop is accelerated sideways, it shrinks sideways. Right? I propose a law: When speed change is caused by time dilation, then there is no contraction related to said speed change. Speed does not change because both time and length shrink by the same factor Link to comment Share on other sites More sharing options...
Toffo Posted October 1, 2013 Share Posted October 1, 2013 Speed does not change because both time and length shrink by the same factor I don't buy that, because some lengths don't shrink. Lengths perpendicular to the motion don't shrink. Let's now compare linear motion and spinning motion: Spinning can be made to appear to become stopped by going into a frame where the spinning object has velocity c. Linear motion of an object can be made to appear to become stopped by going into a frame where the object has velocity 0. The conclusion: spinning and linear motion are fundamentally different kind of things. Link to comment Share on other sites More sharing options...
Endercreeper01 Posted October 1, 2013 Author Share Posted October 1, 2013 I don't buy that, because some lengths don't shrink. Lengths perpendicular to the motion don't shrink. Yes, but there is no part of the velocity perpendicular to the velocity. It shrinks in the direction of motion by a factor of gamma, which is the same with time. The conclusion: spinning and linear motion are fundamentally different kind of things. Yes, but they both can have special relativity applied. Link to comment Share on other sites More sharing options...
Endercreeper01 Posted November 24, 2013 Author Share Posted November 24, 2013 Spinning and linear motion are similar. Spinning motion is just linear motion applied angularly Link to comment Share on other sites More sharing options...
xyzt Posted November 24, 2013 Share Posted November 24, 2013 Spinning and linear motion are similar. Spinning motion is just linear motion applied angularly Mainstream textbooks sharply disagree with the above. Circular motion is characterized by the velocity vector changing direction. Linear motion is exactly the opposite. 1 Link to comment Share on other sites More sharing options...
JVNY Posted December 3, 2013 Share Posted December 3, 2013 Mainstream textbooks sharply disagree with the above. Circular motion is characterized by the velocity vector changing direction. Linear motion is exactly the opposite. Agreed. Consider the Gravitron, the amusement park ride that spins around and subjects riders to 3g force (due to the change of direction from spinning). If that were the same as linear acceleration (speeding up) of 3g's, you would be able to measure relativistic effects on the ride after only a few days of constant spinning. Link to comment Share on other sites More sharing options...
decraig Posted December 22, 2013 Share Posted December 22, 2013 endercreeper dude: In all you escapdes you have not defined once what you mean by :"angular motion" . Would you care to share? Link to comment Share on other sites More sharing options...
Endercreeper01 Posted December 24, 2013 Author Share Posted December 24, 2013 By angular motion, I mean motion moving about an axis or point, such as a spinning object. Link to comment Share on other sites More sharing options...
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