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Answer:
t ≈ 0.590 s (ascent); 5.532 s (descent)
Step-by-step explanation:
We are interested in the values of t when s=16.
s = 30t -4.9t²
4.9t^2 -30t +16 = 0 . . . . . substitute 16 for s; put in standard form
The quadratic formula can be used to find the solutions:
t = (-(-30) ±√((-30)² -4(4.9)(16)))/(2(4.9))
t = (30 ±√586.4)/9.8 ≈ 0.59023, 5.53221 . . . . seconds after launch
a) It will take 0.590 seconds to reach 16 m height initially.
b) It will take 5.532 seconds to return to 16 m height on descent.
