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Physics

A ball is thrown vertically upward, which is the positive direction. A little later it returns to its point of release. The ball is in the air for a total time of 7.99 s. What is its initial velocity? Neglect air resistance.

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  1. v(t) = v(0) + ½ a t

    Given:
    g = -9.8m/s
    t = 7.99s

    Half way up the ball will reach 0 velocity.
    0 = v + ¼ g t

    Alternatively, all the way back, the ball will have a velocity equal but opposite to its initial.
    -v = v + ½ g t

    Use either equation to solve for v.

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  2. Correction:
    use v(t) = v(0) + a t
    v(½ t) = 0, so: 0 = v + ½ g t
    v(t) = -v, so: -v = v + g t

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  3. ijiij

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