Initial velocity: v o = 30 m/s
h = 75 m
h = v o * t + g * t² / 2
75 = 30 · t + 9.8 · t² / 2
75 = 30 t + 4.9 t²
An equation is: y = 4.9 t² + 30 t - 75
4.9 t² + 30 t - 75 = 0
[tex] t_{12}= \frac{-30+/- \sqrt{900+1470} }{9.8}= \\ =\frac{-30+48.68}{9.8} [/tex]
t = 1.9 s
