Motion Along a Straight Line: Calculate velocity of a stream

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Homework Help Overview

The discussion revolves around calculating the velocity of a swimmer in a stream, considering the swimmer's speed relative to the water and the speed of the water current. The problem involves understanding the relationship between these speeds in the context of motion along a straight line.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the equations relating the swimmer's speed and the water's speed, questioning the reasoning behind the established relationships. There is an attempt to clarify how the swimmer's speed upstream is affected by the current.

Discussion Status

The discussion is active, with participants providing insights into the equations used to describe the problem. Some guidance has been offered regarding the interpretation of the swimmer's speed relative to the current, and there is an acknowledgment of a simpler understanding emerging from the conversation.

Contextual Notes

Participants are working under the assumption that the swimmer's speed relative to the water is constant, and there is a focus on the definitions of the speeds involved. The original poster expresses uncertainty about the approach to the problem.

alexsphysics
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Homework Statement
A swimmers speed along the river is 20 km/h and upstream is 8 km/h. Calculate the velocity of the stream and the swimmers possible speed in still water
Relevant Equations
I understand what the variables are and I understand what it is asking to find, but what I'm having trouble with is putting together an equation/formula that will help solve the problem.
Not sure how to go about it
 
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Assuming that the swimmer is swimming at the same speed relative to the water then, writing "u" for the speed of the swimmer, relative to the water and "v" for the speed of the water, then u+ v= 20 and u- v= 8. If you subtract the second equation from the first, 2v= 12 so v= 6 km/h.
 
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Why does u-v=8?
 
Swimming upstream the swimmer is moved backward by the current. If his speed relative to the water is u and the speed of the water is v, then his speed relative to the bank is u- v. In your first post you said "A swimmers speed along the river is 20 km/h and upstream is 8 km/h" so u- v= 8 km/h.
 
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Yes, that is much more simple that I sought out the problem to be for some reason. Thanks a lot!
 

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