Question

The function y = –16t2 + 486 models the height y in feet of a stone t seconds after it is dropped from the edge of a vertical cliff. How long will it take the stone to hit the ground? Round to the nearest hundredth of a second.
Question 7 options:
0.25 seconds
5.51 seconds
11.02 seconds
7.79 seconds

Answer 1

Answer:

5.51 seconds

Step-by-step explanation:

y = 0 when the stone hits the ground. At that point, t can be found from ...

... 0 = -16t^2 +486

... 0 = t^2 -30.375 . . . . divide by -16

... 30.375 = t^2 . . . . . . add the opposite of the constant

Take the square root to get ...

... √30.375 = t ≈ 5.51 . . . . seconds