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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 Website. 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
     
  6. Jan 23, 2009 #5
    Cool thank you very much for your help :D
     
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