physics

Question 1)
A rock is dropped from the top of a 100 meter tall cliff.
A. ) How long will it take for the rock to reach the ground.
B) What will be the velocity of the rock when it hits the ground?
C) How long will it take for the rock to reach the ground if the rock is thrown upward initially at 12 m/s?

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  1. h = -4.9t^2 + 100

    A.
    to reach the ground h = 0
    0 = -4.9t^2 + 100
    4.9t^2 = 100
    t^2 = 100/4.9
    t = √(100/4.9) = appr 4.5 seconds

    B.
    v = -9.8t
    sub in t = 4.5

    C.
    original equation is
    h = -4.9t^2 + 12t + 100
    set equal to zero again, and solve using the quadratic equation. Take the positive result and ignore the negative answer.

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