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 hight of the airplane above ground after t seconds is given by the equation h=-16t^2+56t+1 where h is the hight 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?

A)0.3 seconds
B)1.8 seconds
C)3.5 seconds
D)6.9 seconds
Please Help

Answer 1

The correct answer is B. 1.8 seconds. I just took the test!

Answer 2

h=-16t^2+56t+1, the airplane is shot up from a platform 1 foot above the ground, so 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