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Homework Help: On the Moon the acceleration .

  1. Sep 18, 2005 #1
    On the Moon the acceleration.....

    On the Moon the acceleration of freefall is 1.7 m s-2. How much time would it take for a featherto fall a distance of 1.0m from rest?

    Im not bothered about the answer i just need to know what formula(s) to use
    and how.

    These are the formulas i was given:

    v = u + at
    x = ut + 1/2 at^2
    v^2 = u^2 +2ax
    Average velocity = Displacement / Time
    Average Velocity = (v+u)/2

    u= initial velocity
    a= acceleration
    x= displacement
    v= final velocity
    t= time
    Last edited: Sep 18, 2005
  2. jcsd
  3. Sep 18, 2005 #2


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    But before you can use the formulae, you must understand them, no ?

    What do the formulae mean to you ?

    What values are you given ? What values can you infer, and what do you need to get ?

    There's no point in just pointing out which formula to plug in values into to churn out the answer, that would be like just giving you the answer. You wouldn't learn much from that, I hope you understand.
  4. Sep 18, 2005 #3
    Well you can eliminate the equations that do not give you the information you need.

    For example. V = U + at

    You know what U is (0 m/s) and you know what a is but you don't know V or t.

    So this can't be the equation you need to you use.

    What about [tex] V^2 = U^2 + 2as [/tex]

    Well, once again we know U and a and for that matter s. So we could use this equation to find V and then plug that into the first equation.

    Or Being most sensible you could try

    [tex] x = ut + \frac{1}{2} at^2 [/tex]

    With these questions often the best way to find the answer is to start seeing which ones will give you useful information if you start plugging numbers in.
    Last edited: Sep 18, 2005
  5. Sep 18, 2005 #4
    i got an answer of 0.83 s to 2 d.p. can you tell me if this is correct please
  6. Sep 18, 2005 #5


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    How did you get that (the working) ?
  7. Sep 18, 2005 #6
    the answer is 1.08 i just worked it out properly
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