Question

The time required for the stone to hit the ground is ( ) seconds?

Answer 1

we have the equation

`h=-16t^2+144`

Remember that

when the stone hit the ground, the value of h is zero

so

For h=0

`-16t^2+144=0`

solve the quadratic equation

`\begin{gathered} 16t^2=144 \\ t^2=(144)/(16) \\ t=\pm(12)/(4) \\ t=\pm3 \end{gathered}`

the solution is the positive value

t=3 sec