Answer: 5 Seconds
Step-by-step explanation: Given the equation of the height expressed ad;
h(t) = - 16t^2 + initial height
Given that initial height = 400feet
h(t) = - 16t^2 + 400
The waste will hit the ground at when h(t) = 0
substitute
0 = - 16t^2 + 400
16t^2 = 400
t² = 400/16
t² = 25
t = √25
t = 5secs
