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Physics/Relative velocity

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Question
What is the least time taken to cross a river when the velocity of river is greater than that of the man?

Answer
The velocity of the river is completely immaterial unless you stipulate that it affects (through rough waters) that it affects the velocity of the swimmer.  That's what I assume you mean by "the man."  That leaves the time to be just the width of the river divided by the velocity of the swimmer.  He'll get swept downstream, sure, but that's still the minimum time to cross.

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Dr. Stephen O. Nelson

Expertise

I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

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I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

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Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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