414 algebra De mystif ieD
1
416 60 44 1
4( tt^2 – + ) = () 0
4 t^2 – 15t + 11 = 0
(t − 1)(4t − 11) = 0t
t– =
= 10
14110
411
11
4
275t
t
t
t
.–=
=
=
=The projectile will be 44 feet off the ground at 1 second (on the way up) and
again at 2.75 seconds (on the way down).PRACTICE- An object on the ground is thrown upward at the rate of 25 feet per
second. After how much time will the object hit the ground? - A projectile is fired upward from the ground at the rate of 150 feet
per second. How long will it take the projectile to fall back to the
ground? - An object is thrown upward from the top of a 50-foot building. Its initial
velocity is 20 feet per second. When will the object be 55 feet off the
ground? - A projectile is fired upward from the top of a 36-foot building. Its initial
velocity is 80 feet per second. When will it be 90 feet above the
ground?
✔SOLUTIONS
- In the formula h = −16t^2 + v 0 t + h 0 , v 0 = 25 and h 0 = 0.
h = −16t^2 + 25t
We want to find t when h = 0.
0 = −16t^2 + 25t
0 = t(−16t^2 + 25)
PRACTICE- An object on the ground is thrown upward at the rate of 25 feet per
second. After how much time will the object hit the ground?
PRACTICE- An object on the ground is thrown upward at the rate of 25 feet per