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Math Help - A question about velocity?

  1. #1
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    A question about velocity?

    A baseball player hits a ball. The ball leaves the bat with an initial upward velocity of 35 meters per second. If the ball is 1 meter off the ground when it leaves the bat, about how many seconds will it take for the ball to hit the ground?

    I hate science and this seems to be related to that of an science question...could someone help?
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  2. #2
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    This is a physics problem

    Using conservation of energy...

    K_{i}+U_{i}=K_{f}+U_{f}
    \frac{1}{2}mv_{i}^2+mgh_{o}=\frac{1}{2}mv_{f}^2+0
    v_{i}^2+2gh_{o}=v_{f}^2
    v_{f}=\sqrt{v_{i}^2+2gh_{o}}

    You could also use kinematics but this method is easier
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  3. #3
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    Quote Originally Posted by DrDank View Post
    This is a physics problem

    Using conservation of energy...

    K_{i}+U_{i}=K_{f}+U_{f}
    \frac{1}{2}mv_{i}^2+mgh_{o}=\frac{1}{2}mv_{f}^2+0
    v_{i}^2+2gh_{o}=v_{f}^2
    v_{f}=\sqrt{v_{i}^2+2gh_{o}}

    You could also use kinematics but this method is easier
    Whoa lol confusing.
    7.17 seconds-0.03 seconds 14.34 seconds 35.133 seconds
    I think its 14.34 seconds, any thoughts?
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  4. #4
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    Sorry I misread that won't help you find the time, to find the time...

    if the maximum height is h_{m}
    the initial height is h_{o}=1 meter
    and the final height is h_{f}=0 meters
    and g = -9.8 m/s

    first find the time it takes to reach it's max height , t_{1}

    h_{m}-h_{o}=v_{o}t_{1}+\frac{1}{2}gt_{1}^2 and v_{m}^2=v_{o}^2+2g(h_{m}-h_{o})

    solve these for h_{m}-h_{o} and set equal to eachother,

    v_{o}t_{1}+\frac{1}{2}gt_{1}^2=\frac{v_{m}^2-v_{o}^2}{2g}

    Now solve the quadratic for t_{1}, that's the time it takes to reach its max height.

    That's only a portion of the time the total time is t_{1}+t_{2}, where t_{2} is the falling time
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