Answer:
Part A
1.5 seconds
Part B
By substitution and factorization because h = 0 at ground level
Step-by-step explanation:
Part A
The height from which the soccer player heads the ball, h = 6 feet
The initial velocity of the ball, v = 20 ft./s
The height of the ball in feet, h = -16·t² + 20·t + 6
From the given equation of the ball, we have;
At the initial height, t = 0, from the given equation, h = 6
At the ground level, the height, h = 0, therefore, we get;
0 = -16·t² + 20·t + 6
Factorizing using a graphing calculator gives;
0 = 2 × (-8·t² + 10·t + 3) = -2 × (8·t² - 10·t - 3) = -2 × (2·t -3)·(4·t + 1)
∴ (2·t -3)·(4·t + 1) = 0
t = 1.5 or t = -1/4 = -0.25
Therefore;
The time it takes the ball to hit the ground, t = 1.5 seconds.
Part B
The method used in solving the given quadratic equation is by plugging in the value of 'h' as h = 0 in the given equation and factorizing the result because at ground level, the height, h = 0.
