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Free fall help!

  1. Oct 19, 2009 #1
    1. The problem statement, all variables and given/known data
    a robot probe drops a camara off the rim of a 239 m high cliff on mars, where the freefall acceleration is -3.7 m/s^2. a. fiind the velocity wl wich the camara hits the ground. b. find the tiime required for it to hit the ground.


    2. Relevant equations

    vf^2= vi^2+2ad

    3. The attempt at a solution

    a=-3.7m/s^2
    d=239m
    vi=0m/s
    vf=? ned to find
    t=?

    vf^2=vi^2+2ad
    vf^2=-1786.6
     
  2. jcsd
  3. Oct 19, 2009 #2
    d is actually -239m since it's falling. which means starting from 239 m and falling down to 0m so the change is -239m. the vf you will then calculate is actually negative like the acceleration since, again, it is falling downwards on the y axis
     
  4. Oct 19, 2009 #3
    Looks good except your displacement should be negative, [tex]\Delta d=0-239m[/tex]

    That will make your value for [tex]v_f^2[/tex] positive and you should be able to proceed.
     
  5. Oct 19, 2009 #4
    tyvm!!! but i wanna just ask 1 more question... so then will the final velocity be negative?b/c it is falling
     
  6. Oct 19, 2009 #5
    yes the vf will be negative, like i said in my previous reply >_>
     
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