Answer:
The ball starts at ground level before being kicked, then hits the ground again at t = 4 seconds.
Step-by-step explanation:
Given : Suppose a football is kicked from the ground and its height, h, in feet above the ground is given by [tex]h = -3.9t^2 + 15.6t[/tex]. The time, t, represents the number of seconds after the ball is kicked.
To find : At what time does the football hit the ground?
Solution :
The equation of kicked a football with height and time is given by,
[tex]h = -3.9t^2 + 15.6t[/tex]
We have to find at what time the ball hit the ground which means the height of ball became zero.
So, Substitute h=0 in the equation
[tex]0= -3.9t^2 + 15.6t[/tex]
[tex]t(-3.9t+ 15.6)=0[/tex]
Either t=0 or [tex]-3.9t+ 15.6=0[/tex]
[tex]3.9t=15.6[/tex]
[tex]t=\frac{15.6}{3.9}[/tex]
[tex]t=4[/tex]
The ball starts at ground level before being kicked, then hits the ground again at t = 4 seconds.
