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Homework Help: Find initial velocity given acceleration & distance, no time

  1. Dec 13, 2015 #1
    1. The problem statement, all variables and given/known data
    Frog jumps in air to 1m height. Neglecting air resistance find initial speed the instant it leaves the ground.
    a= -9.8m/s^2
    d= 1m
    vi=?

    2. Relevant equations
    d=1/2(vf+vi)t
    d=1/2at^2 + vi(t) + di

    3. The attempt at a solution
    I figured that since acceleration is 9.8m/s, I could just find time by dividing 9.8m/s by 9.8 and that would give me 1m/0.1s, but that doesn't seem quite right. I then proceeded to put the acceleration, distance, and "time" values into d=1/2at^2 + vi(t) + di, so that vi=0.9m/s^2, but I don't think I did it right. Is there any way to just find initial velocity with only acceleration and distance values?
     
  2. jcsd
  3. Dec 13, 2015 #2

    Buzz Bloom

    User Avatar
    Gold Member

    Hi brendon:

    I think you are missing a useful equation. V2 = 2 a d.

    Hope this helps.

    Regards,
    Buzz
     
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