Answer:
8 seconds
Step-by-step explanation:
Given
h = - 5t² + 40t
When the object hits the ground then h = 0
Substitute h = 0 into the function and solve for t
- 5t² + 40t = 0 ← factor out - 5t from each term
- 5t(t - 8) = 0
Equate each factor to zero and solve for t
- 5t = 0 ⇒ t = 0
t - 8 = 0 ⇒ t = 8
t= 0 denotes the time of launch
t = 8 denotes the time it hits the ground
