Is there a limit of maximum speed in water? Is it a finite value or the speed in water can take any possible value?
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2$\begingroup$ Hi Anjul. Are you asking if there is a maximum speed like the speed of light, or a practical speed limit e.g. because the water will vaporise if you try and move too fast through it? $\endgroup$– John RennieCommented Jul 28, 2017 at 6:09
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$\begingroup$ I am asking about maximum speed limit just like speed of light in vacuum. $\endgroup$– PP_berryCommented Jul 28, 2017 at 6:24
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$\begingroup$ Do you mean the speed of a macroscopic object (like a submarine or a torpedo) moving in water? $\endgroup$– valerioCommented Jul 28, 2017 at 7:30
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$\begingroup$ Nowhere i said the body to be macroscopic or microscopic. $\endgroup$– PP_berryCommented Jul 28, 2017 at 7:57
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1 Answer
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The maximum speed in water is the speed of light in vacuum i.e. $c$.
The speed that light travels in water is less than $c$. It is $c/n$, where $n$ is the refractive index. However this is not any fundamental limitation. It is because light interacts with the electrons present in the water and the interacting light/electron system travels slower than $c$. For more on this see Can speed of light be $c$ in air or other medium? or search this site for many other questions on this subject.
We know that $c/n$ is not the maximum speed in water because subatomic particles can travel faster than $c/n$ in water. This is the origin of Cherenkov radiation.
answered Jul 28, 2017 at 6:57