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Math Help - Another velocity Problem

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    Another velocity Problem

    If a ball is thrown vertically upward with a velocity of 80 ft./s, then its height after t seconds is s = 80t-16t^2.

    a) What is the velocity of the ball when it is 96 feet above the ground on its way up? On its way down?

    I already found in another part of this question that the maximum height is 100 ft. However I think for this I need to set up an inequality, but of what?

    80-32t>96
    -96 -96
    -16(2t+1) > 0

    t > (-1/2) ???????


    80-32t<96


    t < (-1/2) ???????


    I have tried some things but I cant' seem to get any further...
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by qbkr21 View Post
    If a ball is thrown vertically upward with a velocity of 80 ft./s, then its height after t seconds is s = 80t-16t^2.

    a) What is the velocity of the ball when it is 96 feet above the ground on its way up? On its way down?

    I already found in another part of this question that the maximum height is 100 ft. However I think for this I need to set up an inequality, but of what?

    80-32t>96
    -96 -96
    -16(2t+1) > 0

    t > (-1/2) ???????


    80-32t<96


    t < (-1/2) ???????


    I have tried some things but I cant' seem to get any further...
    put s = 96 in the original question and solve for t.

    then plug that t into the velocity function to find the velocity at that time.
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by qbkr21 View Post
    If a ball is thrown vertically upward with a velocity of 80 ft./s, then its height after t seconds is s = 80t-16t^2.

    a) What is the velocity of the ball when it is 96 feet above the ground on its way up? On its way down?

    I already found in another part of this question that the maximum height is 100 ft. However I think for this I need to set up an inequality, but of what?

    80-32t>96
    -96 -96
    -16(2t+1) > 0

    t > (-1/2) ???????


    80-32t<96


    t < (-1/2) ???????


    I have tried some things but I cant' seem to get any further...
    what does "on its way down" mean? the instant it starts to fall? if so, the velocity is zero then
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    Re:

    I take it that the 16 is on the way up and the -16 is on the way down?


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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by qbkr21 View Post
    I take it that the 16 is on the way up and the -16 is on the way down?



    yup, that's right. i guess that's what they mean by on its way down. they mean on its way down when it's at 96 feet.
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    Re:

    Jhevon you are super-Super-Cali-Fragalistitc-Expi-Ali-Docious!!!!!!!!!!!!
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by qbkr21 View Post
    Jhevon you are super-Super-Cali-Fragalistitc-Expi-Ali-Docious!!!!!!!!!!!!
    o stop it
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