Question

A model 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?

Answer 1

3.5 actually

Explanation:

Answer 2

Option B. 1.8 seconds

Explanation:

h=-16t^2+56t+1

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:

`t=-(b)/(2a)`

Replacing the known values:

`t=-(56)/(2(-16))\\ t=-(56)/((-32))\\ t= 1.75`

Approximately 1.8 seconds.

Answer: It takes approximately 1.8 seconds the airplane to reach its maximum height.