Answer :
a. The height of the ball after four seconds is 640 ft
b. The time the ball reachs a height of 768 ft is 6 s or 8 s.
c. The time the ball reachs the ground after it is thrown is 14 seconds.
Since the height of the ball is a parabola, we need to know the equation parabola is
What is a parabola?
A parabola is an equation of the form x(t) = at² + bt + c
a. Height of the ball after four seconds
The height of the ball after four seconds is 640 ft
Since the height of the ball is represented by the equation h(t) = -16t² + 224t. The height of the ball after four seconds is when t = 4.
So, h(t) = -16t² + 224t.
h(4) = -16(4)² + 224(4)
h(4) = -16(16) + 224(4)
h(4) = -256 + 896
h(4) = 640 ft
The height of the ball after four seconds is 640 ft
b. How long will it take the ball to reach a height of 768 ft?
The time it takes the ball to reach a height of 768 ft is 6 s or 8 s.
To find this time, we substituie h = 768 into the equation for the height of the ball.
So, h(t) = -16t² + 224t
768 = -16t² + 224t.
16t² - 224t + 768 = 0
t² - 14t + 48 = 0
Using the quadratic formula, we find t
[tex]t = \frac{-(-14) +/- \sqrt{(-14)^{2} - 4 X 1 X 48} }{2 X 1} \\t = \frac{14 +/- \sqrt{196 - 192} }{2}\\t = \frac{14 +/- \sqrt{4} }{2}\\t = \frac{14 +/- 2 }{2}\\t = \frac{14 + 2 }{2} or t = \frac{14 - 2 }{2}\\t = \frac{16}{2} or t = \frac{12}{2}\\t = 8 or 6[/tex]
So, the time it takes the ball to reach a height of 768 ft is 6 s or 8 s.
c. How long after you throw the ball will it return to the ground?
The time it takes the ball to reach the ground after it is thrown is 14 seconds.
To find the time it takes the ball to reach the ground, the height, h = 0.
So, h(t) = 0
-16t² + 224t = 0
-16t(t - 14) = 0
t(t - 14) = 0
t = 0 or t - 14 = 0
t = 0 or t = 14 s
So, the time it takes the ball to reach the ground after it is thrown is 14 seconds.
Learn more about equation of parabola here:
https://brainly.com/question/25651698
#SPJ1