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: How to find the resultant of 3d vector?

  1. Jul 29, 2010 #1
    i have a vector ai+bj+ck

    is the resultant equal to sqrt(a^2+b^2+c^2). if so how do i explain it mathematically?

    i know the resultant of a 2d vector is equal to sqrt(a^2+b^2) and it can be proved from pythagoras theorem? any ideas??
  2. jcsd
  3. Jul 29, 2010 #2
    That is not resultant that is intensity. Yes if you have vector [tex]\vec{A}[/tex] then

  4. Jul 29, 2010 #3
    first of all, when u say u have a vector ai+bj, sqrt(a^2+b^2) gives u the magnitude of the vector, u shouldn't call it "resultant" as such,
    as far as a 3d vector is concerned u can find its magnitude using Pythagoras theorem only..

    Imagine the vector (a line with the arrow mark) ai+bj+ck, in a xyz space. Then imagine u have drawn a plane consisting the vector and perpendicular to the xy plane, then u can think of a rt triangle OAB being formed with co-ordinates, O(0,0,0); A(a,b,0); and B(a,b,c). The height of the rt triangle is 'b', and its base length is nothing but sqrt(a^2+b^2),[by distance formula]. therefore the length of the hypotenuse of the triangle OAB is sqrt(a^2+b^2+^c).

    this is the magnitude of ur vector ai+bj+ck!!!!!!!!

    i hope u got it!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook