1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: One more Vector problem and we are good to go

  1. Sep 25, 2006 #1
    One more Vector problem and we are good to go!!!

    The Problem:
    Find the change in velocity of a yacht if it changes its velocity from
    5ms^-1 due north to 3ms^-1 due west and also state its direction.

    The solution :
    (resultant vel.)^2 = 5^2 + 3^2 = 5.8 ms^-1
    direction = tan-1(3/5) = 31 degrees west of north

    However , the books answer is 5.8 ms^-1 in a direction 31 degrees west of south . what am i doing wrong here ???
  2. jcsd
  3. Sep 25, 2006 #2


    User Avatar
    Homework Helper

    Draw down the vectors and it should become clear why the direction is 31 degrees west of south. Btw, the change equals [tex]\vec{v}_{2}-\vec{v}_{1}[/tex].

    http://upload.wikimedia.org/wikipedia/commons/thumb/5/5b/Vector_subtraction.png/217px-Vector_subtraction.png" [Broken]
    Last edited by a moderator: May 2, 2017
  4. Sep 25, 2006 #3
    I did draw it but unless south means up and norths means down on paper I dont know what ur getting at lolz I wanna tear my book apart !!!!!!
  5. Sep 25, 2006 #4
    err .... got it !!! im so embarrased !!!

    thank you !!! :)
  6. Sep 25, 2006 #5


    User Avatar
    Homework Helper

    [tex]\vec{v}_{1}[/tex] is pointing north (up). [tex]\vec{v}_{2}[/tex] is pointing west (left). [tex]\vec{v}_{2}-\vec{v}_{1}[/tex] is then pointing south-west.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Similar Threads for more Vector problem Date
Need MORE help with vectors by tomorrow. Oct 27, 2007
More vector help (subtraction) Sep 16, 2007
Vectors and more vectors Sep 9, 2007
More 2D Vector Problems GAK! May 11, 2005
One more vector problem Nov 1, 2003