A bird sitting 16 feet above the ground in an apple tree dislodges an apple. After how many seconds does the apple land on the ground?

Question

my text book gives this equation: h = -16t^2 + vt + s (t = secs, v= vertical velocity, s = initial height)
so i wrote: h = -16t^2 + vt 16

I'm not sure where to go from here.

Answer 1

initial velocity v is zero - it just fell
initial height is 16 feet, so

h = -16t^2 + 16
So, you want to find t when h=0 (apple hits the ground)

-16t^2 + 16 = 0
-16 (t^2-1) = 0
-16(t+1)(t-1) = 0

So, the apple's height is zero when t=1; that is, one second after being dislodged from the tree.

So, what's with the t = -1 solution?
It just means that had the apple been tossed up from the ground, instead of starting from the tree, its launch would have been one second before it had been dislodged.

Answer 2

Thank you, Steve.

Answer 3

I'm workin on the same stuff.. lol

Answer 4

Thanks