Chapter 11 QuaDraTiC appliCaTionS 409
✔SOLUTIONS
For all of these problems, both a negative t and a positive t will be solutions
for the quadratic equations. Only the positive t will be a true solution.
- For the formula h = –16t^2 + v 0 t + h 0 , h 0 = 56 and v 0 = 0 (because the object
is being dropped). The object reaches the ground when h = 0.
h = –16t^2 + 56
0 = –16t^2 + 56
16 t^2 = 56
t^2 =^56
16
t^2 =^7
2
t =^7
2
t≈ 18 7.
The object will reach the water in about 1.87 seconds.
- For the formula h = –16t^2 + v 0 t + h 0 , h 0 = 240 and v 0 = 0 (because the
object is being dropped). The object reaches the ground when h = 0.
h = –16t^2 + 240
0 = –16t^2 + 240
16 t^2 = 240
t^2 =^240
16
t^2 = 15
t = 15
t ≈ 38 7.
The object will reach the ground in about 3.87 seconds. - For the formula h = –16t^2 + v 0 t + h 0 , h 0 = 70 and v 0 = 0 (because the object
is being dropped). The object reaches the ground when h = 0.
h = –16t^2 + 70
0 = –16t^2 + 70
16 t^2 = 70