arocketislaunchedfromgroundlevelwithaninitialvelocityof224ft/s.Whenwilltherocketreachaheightof528ft?先声明不是用528/224

Question

a rocket is launched from ground level with an initial velocity of 224 ft/s.When will the rocket reach a height of 528 ft?
先声明不是用528/224

Answer 1

from the question,we got
initial velocity Vo = 224ft/s upward
height H = 528ft
gravity acceleration g = 9.8m/s^2 = 32.2ft/s^2 downward
from the formular H = Vot- 1/2gt^2
we get the equation:224t - 16.1t^2 = 528
solve equation,we get two answers:3.01s or 10.9s
but the rocket is not like a ball,it won't come back,
and the answer is the less one
so after 3.01 sec the rocket reach a height of 528ft.