Amodel airplane is shot up from a platform 1 foot above the ground with an initial upward velocity of 56 feet per second. the height of the airplane above ground after t seconds is given by the equation , where h is the height of the airplane in feet and t is the time in seconds after it is launched. approximately how long does it take the airplane to reach its maximum height?
Option B. 1.8 seconds
This is a quadratic equation, and its graph is a parabola
h=at^2+bt+c; a=-16, b=56, c=1
Like a=-16<0 the parabola opens downward, and it has a maximum value (height) at the vertex, at the abscissa:
Replacing the known values:
Approximately 1.8 seconds.
It takes approximately 1.8 seconds the airplane to reach its maximum height.
The correct answer is option B. 1.8 seconds. I just took the test.
so it reaches a maximum height of and that happens at
1= - 16t^2+56t+1, we solve this equation
(- 16t+56)t=0, (- 16t+56)=0 or t=o, - 16t+56=0, implies t =3.5s
so the answer is C)3.5 seconds