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Homework Help: How you put gravity in for the equation

  1. Apr 20, 2006 #1
    I realize this probably sounds like a simple question, but I was just wondering how you put gravity in for the equation. I know that gravity is equal to +/-(9.8 m/s^2). However, when you are putting it in an equation such a v=v0+at...do you use 9.8/(t^2) or just the rate...9.8? Thanks in advance for the help:biggrin:
  2. jcsd
  3. Apr 20, 2006 #2


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    You just put in 9.80 m/s^2 where "a" appears in the equation.

    Actually, be careful about the sign. There are different conventions in the litterature.

    Using a y axis pointing up, you may encounter [itex] v_y= v_{y0} + a_y t [/itex] in which case [itex] a_y = -9.80 m /s^2 [/itex] or you may encounter [itex] v_y= v_{y0} - g t [/itex] in whcih case you use g = +9.80 m/s^2.

  4. Apr 20, 2006 #3


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    Since acceleration is a vector quantity, it is always -9.8m/s
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