A ball is thrown downward from the top of a 240​-foot building with an initial velocity of 12 feet per second. The height of the ball h in feet after t seconds is given by the equation h=-16t^2 - 12t + 240. How long after the ball is thrown will it strike the​ ground?

Respuesta :

Answer:

[tex] 16t^2 +12 t -240 =0[/tex]

And we can use the quadratic formula given by:

[tex] t = \frac{-b \pm \sqrt{b^2 -4ac}}{2a}[/tex]

Where [tex] a = 16, b = 12, c =-240[/tex]. And replacing we got:

[tex] t = \frac{-12 \pm \sqrt{(12^2) -4*(16)(-240)}}{2*16}[/tex]

And after solve we got:

[tex] t_1 = 3.516 s , t_2 = -4.266s [/tex]

Since the time cannot be negative our final solution would be [tex] t = 3.516 s[/tex]  

Step-by-step explanation:

We have the following function given:

[tex] h(t) = -16t^2 -12 t +240[/tex]

And we want to find how long after the ball is thrown will it strike the​ ground, so we want to find the value of t that makes the equation of h equal to 0

[tex] 0 = -16t^2 -12 t +240[/tex]

And we can rewrite the expression like this:

[tex] 16t^2 +12 t -240 =0[/tex]

And we can use the quadratic formula given by:

[tex] t = \frac{-b \pm \sqrt{b^2 -4ac}}{2a}[/tex]

Where [tex] a = 16, b = 12, c =-240[/tex]. And replacing we got:

[tex] t = \frac{-12 \pm \sqrt{(12^2) -4*(16)(-240)}}{2*16}[/tex]

And after solve we got:

[tex] t_1 = 3.516 s , t_2 = -4.266s [/tex]

Since the time cannot be negative our final solution would be [tex] t = 3.516 s[/tex]