Answer:
the distance of the object before it hits the ground after launch is t = 1.592 seconds
Step-by-step explanation:
The height of an object launched upward from ground level is given by the function s(t) = -4.9t² +7.8t
when the object reach the ground then s(t) = 0
So; -4.9t² +7.8t = 0
-4.9t² +7.8t + 0 = 0
By using the quadratic equation
[tex]\mathbf{\dfrac{-b \pm \sqrt{b^2-4ac} }{2a}}[/tex]
where; a = -4.9 ; b = 7.8 and c = 0
[tex]\mathbf{=\dfrac{-(7.8) \pm \sqrt{(7.8)^2-4(-4.9)(0)} }{2(-4.9)}}[/tex]
[tex]\mathbf{=\dfrac{-(7.8) \pm \sqrt{(60.84} }{-9.8}}[/tex]
[tex]\mathbf{=\dfrac{-(7.8) + \sqrt{(60.84} }{-9.8} \ \ \ \ OR \ \ \ \ \mathbf{\dfrac{-(7.8) - \sqrt{(60.84} }{-9.8}}}[/tex]
[tex]\mathbf{=0 \ \ \ OR \ \ \ 1.592 }}[/tex]
Hence; the distance of the object before it hits the ground after launch is t = 1.592 seconds