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Math Help - polynomial Inequalities

  1. #1
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    polynomial Inequalities

    The function s(t)= -1/2gt2 +v0t +So can be used to calculate s, the height above a planet's surface in meters, where g is the acceleration due to gravity t is the time in seconds,Vo is the initial velocity in meters per second and so is the initial height in meters. The acceleration due to gravity on mars is g=-3.92 m/s2. Find to two decimal places how long it takes an object to hit the surface of mars if the object is dropped from 1000m above the surface.
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  2. #2
    MHF Contributor ebaines's Avatar
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    Re: polynomial Inequalities

    I don't understand why you titled this thread "polynomial inequalities." From the data you have been given you have s=0m,\ v_o=0 m/s, \ s_0=2000m. So the formula becomes:

     0m = -\frac 1 2 (3.92\frac m {s^2} ) t^2 + 0t +1000m

    Rearrange and solve for t.
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  3. #3
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    Re: polynomial Inequalities

    because thats what it is :/
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  4. #4
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    Re: polynomial Inequalities

    Ok if i solve this using the quadratic formula it is unsolvable
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  5. #5
    MHF Contributor ebaines's Avatar
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    Re: polynomial Inequalities

    Quote Originally Posted by darkangel06 View Post
    Ok if i solve this using the quadratic formula it is unsolvable
    This is simpler than you think, and it's not an inequality:

     0 = - \frac 1 2 (3.92 \frac m {s^2})t^2 +1000

     \frac 1 2 (3.92 \frac m {s^2})t^2 = 1000

     t^2 = \frac { 1000 m} {\frac 1 2 (3.92 \frac m {s^2})}

     t = \sqrt {\frac {2 (1000m)}{3.92 \frac m {s^2}}}

    You can use the quadratic formula if you want to find the roots of at^2 +bt+c = 0, where  a= - \frac 1 2 (3.92), \ b=0,\ c = 1000. Don't forget that minus sign in the 'a' coefficient!
    Last edited by ebaines; October 4th 2013 at 08:12 AM.
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  6. #6
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    Re: polynomial Inequalities

    well g= -3.92 not +3.92
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  7. #7
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    Re: polynomial Inequalities

    Quote Originally Posted by darkangel06 View Post
    well g= -3.92 not +3.92
    if a is acceleration, you would write s = at^2
    if the acceleration is negatinve, as in the gravity, a = -3.92.
    do you see the negative sign in ebaines post.
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