4. How long would it take for a water balloon to fall 39 m if we dropped it starting from rest down an elevator shaft from the 13th floor? Ignore air resistance and use a = -9.8 m/s2.
x, = x + vt + (1/2) a t?

Around 2.8212 sec

Explanation:

Given the eqn x=1/2at^2+vot

your vo=0

39=1/2(-9.8)t^2

=7.95=t^2

=2.82sec

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