What is the Correct Setup for River Relative Velocity Homework?

AI Thread Summary
The discussion focuses on solving a river relative velocity homework problem involving two students canoeing upstream and dropping a bottle. Key equations include the velocity of the canoe relative to the water and the earth, and the velocity of the water relative to the earth. Participants debate the correct interpretation of distances traveled, clarifying that the 2 km and 5 km measurements refer to the earth's frame of reference. A suggestion is made to analyze the problem from the bottle's perspective to simplify the calculation of time. The conversation emphasizes the importance of correctly setting up the problem to find the river's velocity efficiently.
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Homework Statement


Two students are canoeing on a river. While heading upstream, they accidentally drop an empty bottle overboard. They then continue paddling for 1 h, reaching a point 2 Km farther upstream. At this point they realize that the bottle is missing and, driven by ecological awareness, they turn around and head downstream. They catch up with and retrieve the bottle (which has been moving along with the current) 5 Km downstream from the turn-around point.

I am wondering if the setup in my picture is correct. I have my work on there.


Homework Equations





The Attempt at a Solution



Vc/w = velocity of the canoe relative to the water.
Vc/e= velocity of the canoe relative to the earth.
Vw/e= velocity of the water relative to the earth.

Vc/e=Vc/w + Vw/e
 
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There is an easy way to get t2 without any calculation. This allows to get the river velocity quickly, and afterwards the problem is easy to solve.

I disagree with your equations V1=Vc/w and V2=Vc/w. The 2 and 5km refer to earth.
 
mfb said:
There is an easy way to get t2 without any calculation. This allows to get the river velocity quickly, and afterwards the problem is easy to solve.

I disagree with your equations V1=Vc/w and V2=Vc/w. The 2 and 5km refer to earth.

Yeah I messed up. How would you go about getting the time without calculations? By the way I got it.
 
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Consider the problem in the frame of the bottle.
 
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