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!

Is my teacher wrong? Problem dealing with forces.

  1. Jan 14, 2012 #1
    1. The problem statement, all variables and given/known data
    Problem is in the picture


    2. Relevant equations
    The teacher told us the
    Fnetx = 20N - Fx (Fx is 0)
    Fnety = Fy - 50N (Fy = +25N)


    3. The attempt at a solution
    My answer was 32N. But my teacher said the answer was C. which was 77.5N. He got it because Fnety = 75N for him. But that to me doesn't make sense since the Fy and 50N are pointing in opposite directions, won't Fnety be = -25N?
     

    Attached Files:

  2. jcsd
  3. Jan 14, 2012 #2
    Oh nvm i think i got it. I think he meant to put that:
    25N = Fy - 50 huh? Darn and to think i could prove a teacher wrong ;"D
     
  4. Jan 15, 2012 #3

    Redbelly98

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Welcome to PF.
    Glad it worked out finally. The key here was to think carefully about which sign (+ or -) goes with each force -- including Fnety, which we know is + because the object accelerates in the +y direction.
    It pays to be careful -- those forces in parentheses should read (Fnetx is 0) and (Fnety = +25N)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Is my teacher wrong? Problem dealing with forces.
Loading...