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Homework Help: Particle Falling g=1m/s^2 how much time does it take to fall?

  1. Jan 22, 2009 #1
    1. The problem statement, all variables and given/known data

    A particle falls freely through a distance of 1.00 m starting from rest. Assume resume that g = 10
    m/s^2.
    How much time does it take to fall? (4E-1)

    2. Relevant equations

    I think a=vf-vi/t

    3. The attempt at a solution

    I've tried 10m/s^2=1/10m/s-0/t

    And tried to solve for t

    Thanks
     
  2. jcsd
  3. Jan 22, 2009 #2
    Hi Jordash, from the looks of things you are not too familiar with the equations of motion for constant acceleration (often called the SUVAT equations). Here they are in one form:

    [tex]v_f = v_i + at[/tex]
    [tex]s = \frac{(v_f + v_i)}{2}t[/tex]
    [tex]s = v_it + \frac{1}{2}at^2[/tex]
    [tex]s = v_ft - \frac{1}{2}at^2[/tex]
    [tex]v_f^2 = v_i^2 + 2as[/tex]

    where s is displacment, and for the purposes of you question you can consider that the distance traveled by the particle. So now thats all you need to solve this problem, have a real think about what you know about the particle, dont make any assumptions and only use values that you can gather from the question, I will say that you thought that the final velocity of the particle was 0.1ms-1, now that isnt correct as it is not as simple as deviding the distance by the acceleration. Pehaps using these equations you could also work out the correct final velocity ;-)
     
  4. Jan 22, 2009 #3
    Ok, let me know if i'm heading in the right direction with this, I used the equation above:

    s=v_it+1/2at^2

    And I got to here:

    1m=0+1/2*10m/s^2*t^2

    1m=5m/s^2*t^2
    1m/5m/s^2=t^2

    So now I need to find what t = by solving for t^2=1/5 if i'm doing it right? I hope I did it right.

    Which comes out to about: .45 seconds, is that right?

    Sorry I don't know how to use Latex :(

    Thank you very much for the excellent list and your help.
     
  5. Jan 23, 2009 #4
    Hey Jordash, perfect, congrat on the answer. And thats no problem about the latex, although if you do want to post more around these forums you might like to learn a bit for simple equations, it really isnt hard to do, infact the equations you wrote are almost in latex :D

    Dont feel obligated to do so, but if you would like to learn a bit of latex you could try this http://www.sitmo.com/latex/". You can code some latex or select the symbols which shows you the code, and it shows you what it looks like in real time ;-)

    Oh and also this forum has a built in Latex help, if you click this symbol:

    [tex]\sum[/tex]

    when you are in the reply/edit post screen, if brings up a list of all the latex "things" you can do :D
     
    Last edited by a moderator: Apr 24, 2017
  6. Jan 23, 2009 #5
    Cool thank you very much for your help :D
     
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