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Volcano in mars ejects rocks. Straight line motion

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  1. Jan 19, 2013 #1
    1. The problem statement, all variables and given/known data

    A certain volcano on earth can eject rocks vertically to a maximum height .

    Part A: How high (in terms of H ) would these rocks go if a volcano on Mars ejected them with the same initial velocity? The acceleration due to gravity on Mars is 3.71 m/s^2 , and you can neglect air resistance on both planets.


    2. Relevant equations

    y=yo + vo*t + 1/2 *g*t^(2)

    vy=vo + g*t

    3. The attempt at a solution

    y=yo + vo*t - 1/2 *g*t^(2)


    vy=vo + g*t
    0=vo-g(mars)*t

    t=vo/g
    substitute this in y=yo + vo*t - 1/2 *g*t^(2)

    to get y=1/2 * vo^(2)/g

    After this I am stuck. The answer is 2.64H or 2.64Y


    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jan 19, 2013 #2

    Dick

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    g on Earth is 9.8m/s^2. What's the ratio of y=1/2 * vo^(2)/g between Mars and Earth?
     
  4. Jan 19, 2013 #3
    Ah I see now thanks. However how do you know when to take the ratio? I did not even think about that.
     
  5. Jan 19, 2013 #4

    Dick

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    The height on earth is H=(1/2)v0^2/(9.8m/s^2). The height on Mars will be (1/2)v0^2/(3.71m/s^2). If you divide the two then everything will cancel except for the ratio of the two values of g.
     
  6. Jan 19, 2013 #5
    Got it and thank you.
     
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