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Let's say that I have some type of long bar. It is perfectly incompressible. On one side I have a sensor that detects any force. On the other end, I hit the bar with a hammer. From the moment my hammer hits this bar and the moment my force transducer picks up the force on the other end should be instantaneous right? Why would this scenario be any slower than the speed of light?

Qmechanic
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Raven
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  • No poles exist which are perfectly incompressible - that's the basic problem. If there was an incompressible substance, then mechanical energy would propagate along it instantly. – Steve Mar 01 '18 at 00:08
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    @Steve, What you say is true because the hammer blow on any solid object made out of atoms will be transmitted to the other end of the bar, atom-by-atom, as a sound wave. But, focusing on that truth hides a deeper truth: In order to accept the Theory of Relativity, you must accept that no signal can travel faster than light. If you accept that no signal can travel faster than light, then you must conclude that a "perfectly incompressible" object can not exist, no matter what it might be made of. – Solomon Slow Mar 01 '18 at 02:23

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In this you should have concept about wave.As you hit on one side, particels of the bar would oscillate. Then a wave in those particles would be orginated.This wave would transfer the force to other terminal.Time of transferring to other end depends on the wave’s velocity which is propotional to force.If you apply more force,the wave velocity will be more but not more than the speed of light.Because if you want to get equal speed of light, it will requried more and more and more force which is out of our think.In real life this wave speed is approximately 5000 m/s(If the bar is of iron) < 300000000 m/s

Mhm Mehedi
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    That isn't true. The velocity of a disturbance propagating through a solid is not proportional to the initial impulse. – J. Murray Feb 28 '18 at 21:09
  • Why? If you force, more particles will oscillate more and then the speed will be more – Mhm Mehedi Feb 28 '18 at 21:16
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    What you say is simply not true, for the same reason that loud sounds do not travel faster than quiet sounds. The propagation speed of elastic waves through a medium is determined by the medium's density and bulk modulus - see, for example, here. – J. Murray Feb 28 '18 at 21:20