Question

3. A soccer player heads a ball from a height of 6 feet with an initial vertical velocity of

20 feet per second. The height h in feet of the ball is given by h = -167 + 20t +6,
where t is the time elapsed in seconds. How long will it take the ball to hit the
ground if no other players touch it? State the method you used to solve this
quadratic equation and why you chose that method.

Answer 1

1.5secs

Explanation:

Given the expression that models the height as;

h(t) = -16t²+20t +6

The ball will touch the ground at when h(t) = 0

0 = -16t²+20t +6

Swap

-16t²+20t +6 = 0

Divide through by -2

8t²-10t-3 = 0

Expand using the general formula

t = -(-10)±√(-10)²-4(8)(-3)/2(8)

t = 10±√100+96/16

t = 10±√196/16

t = 10±14/16

t = 10+14/16

t = 24/16

t = 1.5

Hence it will take the ball 1.5secs to hit the ground