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haynewp
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What if the center part of a bicycle wheel was spinning at almost the speed of light. What would keep the outside part of the rim from spinning faster than the speed of light?
haynewp said:What if the center part of a bicycle wheel was spinning at almost the speed of light. What would keep the outside part of the rim from spinning faster than the speed of light?
Yes, but in flat space it's impossible for the circumference of a wheel to shrink without its radius shrinking by the same amount. The spokes will not be Lorentz-contracted, but if they're compressible they'll be pushed down by the shrinking rim.Zanket said:It's the circumference that is length-contracted in this case (from the perspective of a stationary observer), not the radius. Presumably the rim is intact regardless.
JesseM said:Yes, but in flat space it's impossible for the circumference of a wheel to shrink without its radius shrinking by the same amount. The spokes will not be Lorentz-contracted, but if they're compressible they'll be pushed down by the shrinking rim.
If you consider things from the point of view of someone on the wheel, you're dealing with a non-inertial coordinate system where the laws of physics (including those relating to Lorentz contractions) won't work the same way they do in an inertial coordinate system. You could also just consider the inertial frame where the guy on the wheel is instantaneously at rest at a given moment, but at that same moment other parts of the wheel will be in motion, so different sections of the rim will be contracted by different amounts in this frame. I'm not saying Lorentz contraction is the only thing you need to explain why the rim can never exceed the speed of light--the most basic explanation is just that it would take an infinite amount of energy to accelerate any point on the wheel to FTL speeds, and that there can be no such thing as a perfectly rigid object in relativity.wangyi said:I don't think Lorentz contration can help, because, first, for the person lives on the wheel and rotates with it, there is no velocity relative to the wheel, and it can be him, not the people standing on the Earth accelearate the wheel.
Just consider the free fall frame where the center of the wheel is at rest (though still rotating). In this frame, every point on the rim is moving with the same velocity.wangyi said:second, if you consider
rigorous on this question, it is not at a free fall frame, and the Lorentz contration can not be used to measure the contration of a rotating object.
A spinning wheel is a mechanical device that rotates rapidly around a central axis. It works by using a motor or other power source to provide energy, which is then used to spin the wheel. The spinning motion can be used for various purposes, such as powering machinery or creating energy.
Light speed is important in relation to a spinning wheel because it determines the maximum speed at which the wheel can rotate. If the wheel were to spin faster than light speed, it would violate the laws of physics and be impossible to achieve.
The relationship between a spinning wheel and light speed is that the speed of light is the fastest possible speed that any object, including a spinning wheel, can travel. This is known as the speed limit of the universe and it plays a crucial role in many aspects of physics and technology.
No, a spinning wheel cannot reach light speed. According to Einstein's theory of relativity, the closer an object gets to the speed of light, the more energy is required to accelerate it further. At the speed of light, an infinite amount of energy would be needed, which is impossible to achieve. Therefore, a spinning wheel can never reach light speed.
Time dilation is the concept that time appears to pass slower for objects that are moving at high speeds. This means that for a spinning wheel that is approaching light speed, time would appear to pass slower for the wheel compared to an observer who is not moving at such a high speed. This effect is very small at everyday speeds but becomes significant as an object approaches light speed.