Optimizing Swimming Across a River: Upstream, Downstream, or Directly Across?

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SUMMARY

To swim across a river in the shortest time, one should aim slightly downstream rather than directly across or upstream. This strategy utilizes the river's current, allowing the swimmer to benefit from the flow instead of fighting against it. The relevant equation for this scenario is v_b = v_{br} + v_r, where v_b is the swimmer's velocity, v_{br} is the swimmer's velocity relative to the river, and v_r is the river's velocity. The swimmer's time to cross is minimized when the vertical component of their velocity, v_{b_y}, is maximized.

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Homework Statement


If you were trying to swim across a river with the shortest possible time, would you aim your body slightly upstream, directly across the river, or slightly downstream? Explain.

Homework Equations


no equation needed

The Attempt at a Solution


i feel the answer is downstream because you go with the flow of the water and you aren't fighting against the current like you would in the upstream motion.
 
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hafsa786786786 said:

Homework Statement


If you were trying to swim across a river with the shortest possible time, would you aim your body slightly upstream, directly across the river, or slightly downstream? Explain.

Homework Equations


no equation needed

The Attempt at a Solution


i feel the answer is downstream because you go with the flow of the water and you aren't fighting against the current like you would in the upstream motion.
Okay, what might you do to confirm your hypothesis?
 
you can make use of these equations:
##v_b=v_{br}+v_r##
if velocity of river is vr along +x direction and vbr is thr velocity of boat with respect to river.
the component of v_b along y direction comes out to be dependent only on v_br.Try it.
Now time ##t=w/v_{b_y}## where w is the width of the river.
so you wil have minimum time when v_by is maximum.
 

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