Needs clarity on this displacement vector diagram

  • #1
Chijioke
14
3
Homework Statement
How far from his destination
Relevant Equations
The trigonometric ratios of acute angles in a right angled triangle:
SOH CAH TOA
IMG_20230831_042607.jpg

The problem is actually a solved example
IMG_20230901_042351.jpg

My attention is focused in understanding the displacement vector diagram as it has to deal with question (iv).
I have no problem understanding the velocity vector sketch below:
velocity vector.png


As you can see ND is the velocity of the river current due East and NE is the velocity of the boat supposed the man chooses to go Northward.
Here comes another sketch for the velocity
displacement vector original.png

I am confused about the sketch because
a. I don't understand what the vertical arrow beside NA meant.
b. the 3km, is what? Is the displacement of the river or what? If it is, how was obtained because I know from the wording of the problem nothing like that was given. what was given 3 kmhr-1, which the displacement of the river. From the solving as it in the book I thinking that the 5km
IMG_20230901_043519.jpg


As I showed here
displacement vector (1).png

Please help my understanding. Thank you.
 

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  • #2
Chijioke said:
I am confused about the sketch because
a. I don't understand what the vertical arrow beside NA meant.
b. the 3km, is what? Is the displacement of the river or what? If it is, how was obtained because I know from the wording of the problem nothing like that was given. what was given 3 kmhr-1, which the displacement of the river. From the solving as it in the book I thinking that the 5km
You are understandably confused because the diagram provided in the solution is mislabeled. The vertical arrow beside NA must represent the vertical component of the displacement which is given as 5 km. The label 3 km is either a typo or the drawing is pasted from a different problem. Your drawing of the displacement vector is correct.
 
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  • #3
kuruman said:
You are understandably confused because the diagram provided in the solution is mislabeled. The vertical arrow beside NA must represent the vertical component of the displacement which is given as 5 km. The label 3 km is either a typo or the drawing is pasted from a different problem. Your drawing of the displacement vector is correct.
I may still have question concerning this but let go and think. Thank you.
 
  • #4
Chijioke said:
I am confused about the sketch because
a. I don't understand what the vertical arrow beside NA meant.
The river can't be made narrower: the man still has 5 km separating him from the opposite shore.
It must be a typo.
 
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