The height above ground in feet of a toy rocket launched upw
The height above ground, in feet, of a toy rocket launched upward from the top of a building is given by s(t) = 16t2 + 64t + 192.
(a) What is the height of the building? ft
(b) What is the maximum height attained by the rocket? ft
(c) Find the time when the rocket strikes the ground. s
Solution
s(t) = -16t^2 + 64 t + 192
a) for height of the building plug t = 0
s(t) = -16(0)^2 + 64(0) + 192
s(t) = 192 feet
height of the building = 192 feet
b) maximum height is the vertex of the equation
plug t = -64 / 2*-16 = 2 in the equation
-16(2)^2 + 64(2) + 192 = 256 feet
maximum height = 256 feet
c) time when rocket strikes tyhe ground plug s(t) = 0 and solve for t
-16t^2 + 64 t + 192 = 0
or dividing the entire equatio by -16
t^2 - 4t - 12 = 0
( t - 6 ) ( t+ 2) = 0
t = 6 seconds
rocket strikes the ground after 6 seconds
