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Math Help - 2 formulas, when do they match...

  1. #1
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    2 formulas, when do they match...

    Hello everyone.
    I have 2 formulas, derived from horizontal and vertical position;
    V=(4.92t^2 - 1.8)/0.8t
    V=√2/0.6t
    The question was a projectile motion question to find what velocity a high jumper needed to be travelling at to make a jump of 1.8 metres that was √2 metres away launching at 53degrees. I worked out the 2 positions equations having the same V then created these 2 formulas from there. Not sure what to do from here.. Please help!
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  2. #2
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    Re: 2 formulas, when do they match...

    Check the signs in the first equation.
    If you take g negative, h and V*sinθ are positive and the equation becomes
    h = V*sinθ*t - 1/2*g*t^2. so the V will be
    V=(4.92t^2 + 1.8)/0.8t
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  3. #3
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    Re: 2 formulas, when do they match...

    Okay so i have those signs switched, said they equal each other, but i cant seem to get a t value?
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  4. #4
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    Re: 2 formulas, when do they match...

    V=√2/0.6t = (4.92t^2 + 1.8)/0.8t

    √2*0.8t/0.6t = (4.92t^2 + 1.8)

    √2*0.8/0.6 = (4.92t^2 + 1.8)

    Now solve for t.
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  5. #5
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    Re: 2 formulas, when do they match...

    Got it thanks Discovered my problem was just rounding too much, so when i solved i always got t=0..
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