Question

if s= -16t^2+ 144t represents the height of a rocket, in feet, t seconds after it was fired, when will the rocket hit the ground? (hint: The rocket is on the ground when S = 0).The rocket will hit the ground after ? seconds

Answer 1

It is given that:

`s=-16t^2+144t`

It is said to find the time when the rocket hits the ground and s is the height of rocket.

When the rocket hits the ground, s=0.

`\begin{gathered} 0=-16t^2+144t \\ t(-16t+144)=0 \\ t=0,t=(144)/(16)=9 \end{gathered}`

Hence time is either 0 or 9 seconds. Hence after the rocket is in the air it will hit the ground after 9 seconds.