Question

A pinecone drops from a tree branch that is 20 feet above the ground. The function h = –16t2 + 20 is used. If the height h of the pinecone is in feet after t seconds, at about what time does the pinecone hit the ground?

Answer 1

Answer:

  t ≈ 1.118 . . . seconds

Step-by-step explanation:

Set h=0 and solve for t.

  0 = -16t^2 +20

  0 = t^2 -20/16 . . . . . . . . . . . . . . . divide by the coefficient of t^2

  t = √(5/4) = (1/2)√5 ≈ 1.118 . . . . . add 5/4 and take the square root

The pinecone hits the ground about 1.12 seconds after it drops.