Magnitude and Direction, Canoe on River

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Homework Help Overview

The problem involves determining the velocity of a canoe relative to a river, given the canoe's velocity relative to the earth and the river's velocity. The subject area is vector addition in physics, particularly in the context of motion in two dimensions.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the magnitude of the canoe's velocity and express uncertainty about calculating the angle relative to east. Questions arise regarding the interpretation of the direction "southwest" and how it relates to vector components.

Discussion Status

The discussion is ongoing, with participants sharing their attempts and questioning the methods for finding the angle. Some guidance has been offered regarding vector addition and determining angles from components, but no consensus or complete solution has emerged.

Contextual Notes

There is mention of constraints regarding the complexity of the problem, with one participant noting that the teacher provided a velocity answer deemed too complicated for their level. This suggests a potential gap in foundational knowledge that is being explored in the discussion.

ap_physics
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Homework Statement


A canoe has a velocity of 0.35 m/s southwest relative to the earth. The canoe is on a river that is flowing 0.65 m/s east relative to the earth. Find the velocity (magnitude and direction) of the canoe relative to the river.

The Attempt at a Solution


0.930985 is the magnitude.
Then I have no clue how to get the angle in terms of counterclockwise from east.

Thanks very much in advance!
 
Last edited:
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ap_physics said:

Homework Statement


A canoe has a velocity of 0.35 m/s southwest relative to the earth. The canoe is on a river that is flowing 0.65 m/s east relative to the earth. Find the velocity (magnitude and direction) of the canoe relative to the river.

The Attempt at a Solution


0.930985 is the magnitude.
Then I have no clue how to get the angle in terms of counterclockwise from east.

Thanks very much in advance!

Hi ap_physics; Welcome to Physics Forums.

How did you arrive at an angle of 315 degrees for the canoe's velocity? I would have thought that "southwest" would be halfway between south and west.

Edit: I see you've edited your original so that the angles of the vectors are no longer shown. Perhaps you could just explain your approach to the problem?
 
Well, I posted my attempt earlier, but it was wrong, and I was given the answer for the velocity by my teacher, as it was too complicated for our level. But, he says I can still find the angle. But, I don't know which formula to use.
 
ap_physics said:
Well, I posted my attempt earlier, but it was wrong, and I was given the answer for the velocity by my teacher, as it was too complicated for our level. But, he says I can still find the angle. But, I don't know which formula to use.

Okay, what have you learned so far about adding and subtracting vectors? Have you learned how to determine their angles from their x and y components?
 

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