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: Question on a ramp

  1. Jan 31, 2006 #1
    I have a 1kg weight on a rmap inclined 20degrees being pulled upwards and to the left
    *******-
    ***********-
    ************** -
    ******************-
    in that motion above(look at dashes only), is it -ma or +ma?
    so the equation is

    -a = t - mgsin20
    or
    a = t - mgsin20
    im just wondering if a leeft movement has anythign to do with gravity (A) being + or-
    thanks
     
    Last edited: Jan 31, 2006
  2. jcsd
  3. Jan 31, 2006 #2
    try looking at it in terms of the forces acting in the X direction and the forces acting in the Y direction. Consider where you place your origin.

    Then think about which vectors will be positive and which will be negative.
     
  4. Jan 31, 2006 #3
    no no i just want a simple anaswre
    i just meant weather acceleration should be -ma or +ma
     
  5. Jan 31, 2006 #4
    It has to do with how you define coordinate system.
     
  6. Jan 31, 2006 #5
    i have an exam tomorrow and i just wanted to know , are you saying theres no way to tell from the info i sent?
    *sigh* nvm..
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook