Relative velocity boat crossing a river

  • Thread starter Woolyabyss
  • Start date
  • #1
143
1

Homework Statement


A boat crosses river, 240 m wide,which flows parallel to the straight banks with velocity
v1 = 12i, while the velocity of the boat relative to the river is v2 = 5j where v1 and v2 are measure in m/s

(i) find the magnitude of the actual velocity of the boat.

(ii) find how long it takes the boat to cross the river and the distance it has travelled downstream in doing so

Homework Equations





The Attempt at a Solution


(i)(12^2 + 5^2)^(1/2) = 13 m/s

(ii) relative distance/relative speed = 240/5 =48 s

48(12) =576 m

can somebody tell if part (ii) is right the back of my book seems to use 12 as the relative speed since it says it takes 20 seconds.
Any help would be appreciated.
 

Answers and Replies

  • #2
ehild
Homework Helper
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1,897
Your solution is correct.

ehild
 
  • #3
tiny-tim
Science Advisor
Homework Helper
25,832
251
yes, it looks as if the book has got the 12 and the 5 the wrong way round :redface:
 
  • #4
143
1
Thanks.
 

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