Help! river crossing confusion =(

  • Thread starter j_confused
  • Start date
  • #1
Woo. Nevermind the rest of this message. I figured it out =))))



Hello all :)

Am having brain fart, I need help (obiviously) from the experts! All the tutorials and examples about the classic boat crossing a river aren't helping me with this problem.

"A woman can row a boat at 6.3 km/h in still water. (Assume i points to the far side of the river, perpendicular to the current, and j points in the direction of the current.)"

At this point, I drew a diagram. As for vectors, i is 105 m/min [answers require meters/minutes] perpendicular to shore, I assumed current to be heading east (downriver in my drawing).
___________________________________
......^.........105 m/min i.......................|
......| ............................................5500m
......|................................................|
.....--------> 0 m/min j....................|

This makes sense, b/c it would take roughly 52 mins to cross to a point directly across. Then comes the confusing bits.....

(a) If she is crossing a river where the current is 3.2 km/h, in what direction must her boat be headed if she wants to reach a point directly opposite her starting point? (in degrees)

(b) How long will it take her to cross the river? (in minutes)


Based on the above, i is still 105 m/min and j is now ~53.3 m/min, so the resultant would be 117.5 m/min.... I think.
From there, I'm lost. Please help!

-Jen
 
Last edited:

Answers and Replies

  • #2
16
0
90 degrees- tan-1(6.3/3.2)

is the angle
 
  • #3
16
0
what your email and ill send you a good diagram
 

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