Question

The height, h, in metres, of a rocket t seconds after it is launched is approximately modelled by the quadratic relation h = 80t - 16t2. To the nearest second, how long is the rocket in the air?

Answer 1

Answer: 5 s

Step-by-step explanation:

Given

Height of the rocket can be modelled as $h=80-16t^2$

Rocket will land on earth when it's height becomes 0

$\Rightarrow 80t-16t^2=0\\\Rightarrow t(80-16t)=0\\\\\Rightarrow t=0\ \text{or}\ t=\dfrac{80}{16}=5\ s$

Neglecting 0 value

Thus, rocket remains in air for 5 s.