Answer:
The ball hits the ground after 7 seconds.
The ball is thrown from a height of 140 ft.
The ball reaches a maximum height of 320 ft, which occurs at 3 seconds.
Step-by-step explanation:
The easiest and fastest way to do this is to graph the equation in a graphing calc. When t = 0, we know that would be the y-intercept and we would find the initial height of the ball. The maximum vertex of the graph would be the maximum height of the ball (y-value) and where the graph crosses the x-axis would be where the ball hits the ground.
Answer:
Step-by-step explanation:
the ball hits the ground when h=0
0=-20 t²+120 t+140
or t²-6t-7=0
t²-7t+t-7=0
t(t-7)+1(t-7)=0
(t-7)(t+1)=0
t=7,-1(rejected)
after 7 seconds the ball hits the ground.
when t=0,h=140
ball is thrown from a height of 140 ft
(c)
h=-20t²+120t+140
=-20(t²-6t+3²-3²)+140
=-20(t-3)²-20×-9+140
=-20(t-3)²+180+140
=-20(t-3)²+320
max. height is reached =320 ft
