Chapter 11 QuaDraTiC appliCaTionS 415
–+ 16 tt = 25 = 00 ( Thisiswhentheobjectisthhrown.
–= –
= –
- =
=
)
.
16 25
25
16
25
16
1 5625
t
t
t
t
The object will hit the ground after 1.5625 seconds.
- In the formula h = −16t^2 + v 0 t + h 0 , v 0 = 150 and h 0 = 0.
h = −16t^2 + 150t
We want to find t when h = 0.
016 150
016 150
16 150 0
2
( )
= –+
= –+
–+ =
tt
tt
tt = (.Thisiswhen theprojectileisfired)
0
16 tt
t
t
t
.
= –
= –
- =
=
150
150
16
75
8
9 375
The object will fall back to the ground after 9.375 seconds.
- In the formula h = −16t^2 + v 0 t + h 0 , v 0 = 20 and h 0 = 50.
h = −16t^2 + 20t + 50
We want to find t when h = 55.
55 = −16t^2 + 20t + 50
0 = −16t^2 + 20t − 5
t ()()( )
()
= –± – ––
(^20204165) = –± –
216
(^2204003220)
32
20 80
32
20 894
32
035090
- = –±
≈ –±
≈
. ., .