1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Resultant vector given initial velocity and acceleration

  1. Feb 8, 2013 #1
    1. The problem statement, all variables and given/known data


    There can be more than one right answer

    2. Relevant equations

    v = v0 + αt

    3. The attempt at a solution

    Im having difficulty understanding the upward acceleration vector. Because I set the +y direction as positive (up) and the +x-direction as positive (right). So I thought that if acceleration is up, it means that acceleration is positive so the velocity is increasing (just a vector that is the exact same as the Vo vector).
    I attempted to add the two vectors together (hypotenuse) and say that was the answer, but it was incorrect (45° angle vector).
    Last edited: Feb 8, 2013
  2. jcsd
  3. Feb 8, 2013 #2


    User Avatar

    You can't add an acceleration vector to a velocity vector; they have different units. And since you don't have any magnitudes and don't know how long the force acted, you are looking for a qualitative answer, not a quantitative one (that is, you couldn't have gotten a 45 degree angle). You are on the right track, though. Look at the possible answers and see if you can eliminate any of them.
  4. Feb 8, 2013 #3
    thanks for the reply tms,
    I guess my question then is, how am I supposed to add two unlike vectors?
    So far, I eliminated A because I believe it doesn't make sense for there not to be a velocity vector.
    C seems unlikely because of the initial velocity
    E seems unlikely because that straight vector pointed right doesnt have the acceleration acting on it.
    Would the answer be B and D, because they are the only resulting vectors that have the depicted upward acceleration acting on them with still pointing to the positive X-direction?
  5. Feb 8, 2013 #4


    User Avatar

    You don't need exact results, just a general idea of what the effects of the force would be.
  6. Feb 8, 2013 #5
    ... I swear I attempted that solution D:, but I tried it again and it worked! I think I accidentally submitted my response incorrectly!

    Thank you tms for your help! (I was on my last attempt)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook