Answer:
5.25 seconds
Step-by-step explanation:
When the ball hits the ground the height is zero
Equate f(t) to zero and solve for t , that is
- 16t² + 84t = 0 ← factor out - 4t from each term
- 4t(4t - 21) = 0
Equate each factor to zero and solve for t
- 4t = 0 ⇒ t = 0
4t - 21 = 0 ⇒ 4t = 21 ⇒ t = [tex]\frac{21}{4}[/tex] = 5.25
t = 0 is the time when the ball is kicked
t = 5.25 is the time taken for the ball to hit the ground
