What is the solution to this relative motion problem?

AI Thread Summary
The discussion centers on a relative motion problem involving a man trying to cross a river and end up directly opposite his starting point. The initial interpretation suggests he should move straight west, but the river's current will push him north, requiring him to adjust his angle. One participant believes the correct answer is 8.0 km/h west, while another argues for a different solution. The confusion arises from the distinction between intended direction and actual ground velocity. Ultimately, the problem highlights the complexities of navigating motion in a current.
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Homework Statement


http://img221.imageshack.us/img221/5571/kinematicslz1.jpg
I asked my teacher to clarify this question a bit more, and she said that the man wanted to end up exactly opposite to where he was on the west shore, or in other words, parallel to where he was from the east shore.

Homework Equations


soh cah toa
a^{2} + b^2 = c^2


The Attempt at a Solution


I think that the answer is B), because in order for him to end up exactly opposite of where he is, he must go west.
However, my teacher thinks that the answer is D). Who's right?
 
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Can anyone help?
 
If he goes straight west, he won't land directly opposite of his starting position, since the river will have pushed him north. Therefore he must travel at some angle south of west.
 
Sorry, I meant to say that the man wanted to go straight west, so he had to go 10kkm/h at an angle. But the question is asking for the actual velocity, or in other words, the ground velocity, which is, as I think, 8.0 km/h west.
 
Yes, I suppose it depends on your interpretation of the question then.
 
Well it says actual motion.
 

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