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: Vectors and Acceleration

  1. Sep 16, 2008 #1
    1. The problem statement, all variables and given/known data
    Three forces in the x-y plane act on a 3.40 kg mass: 9.10 N directed at 25o, 12.40 N directed at 156o, and 4.70 N directed at 259o. All angles are measured from the positive x-axis, with positive angles in the Counter-Clockwise direction. Calculate the magnitude of the acceleration.

    2. Relevant equations

    Rx = F1cos(theta) - Quadrant 1
    Ry = F1sin(theta) - Quadrant 1
    R = (Rx^2 + Ry^2)^1/2

    3. The attempt at a solution

    I tried to find the x and y components of each force. Then I added the square of the x-components and took the square root of that answer and I did the same with the y-components. Finally I took the answers from the last step and took the square of them and then the square root of them added. Finally I plugged in that force into F=ma and tried to solve for a, but it doesnt work. I think Im doing something wrong, in that Im not sure what to do about the x,y components that are negative.
  2. jcsd
  3. Sep 17, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi ganondorf29! :smile:
    ah … that's where you're going wrong …

    these are vectors, so you use ordinary vector addition …

    just add the x-components without squaring first. :smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook