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!

Help with physics:vectors

  1. May 19, 2005 #1
    alright ive been stuck on these problems for the entire day. my teacher give us online homework, called mastering physics. the problem says to find the angle of each of the vectors.

    A=Ax+Ay and B=Bx+By

    they give me for for vector A, Ax=-1.40,Ay=4.2. now vector B, Bx=1.2,By=-2.6

    so i pluged in, 108,204 and it comes back saying that my answer is off by an additive constant? what does that mean? ive tried looking at online tutorials but nothing explained what i did wrong. the answer is suppose to be in degrees. :frown: im getting really agitated :cry:
  2. jcsd
  3. May 19, 2005 #2


    User Avatar
    Science Advisor
    Homework Helper


    [tex]\vec{A}\cdot\vec{B} [/tex]

  4. May 19, 2005 #3
    ive tried the scalar product rule and still it doesnt work.
  5. May 19, 2005 #4
    There are 2 equivalent ways of calculating a dot product.

    [tex]\vec{A} \cdot \vec{B} = A B \cos \theta = A_x B_x + A_y B_y + A_z B_z[/tex]

    Where [tex]A[/tex] is simply the magnitude of the vector [tex]\vec A[/tex]. Does that give you an idea now?
  6. May 19, 2005 #5
    I'm betting you forgot the negatives.
  7. May 19, 2005 #6
    lmao i did forget the negative. :( but thanks alot for your help guys. and this is a very cool site
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Help physics vectors Date
Calculating tensions in ropes suspending an onject Jun 11, 2017
Acceleration Vector Word Problem Mar 19, 2017
Adding Vectors using Cefore Method Nov 16, 2016