Question 507332
 {{{s = 16t^2 + 32t}}} where {{{s}}} is in feet  

How long (nearest tenth) will it take the ball to fall {{{233ft}}}

start with:


{{{s = 16t^2 + 32t}}} ...plug in {{{s}}}


{{{233ft = 16t^2 + 32t}}} ..........solve for {{{t}}} 


{{{ 16t^2 + 32t-233 =0}}}


{{{t = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}


{{{t = (-32 +- sqrt( 32^2-4*16*(233) ))/(2*16) }}}


{{{t = (-32 +- sqrt( 1024+14912 ))/32 }}}


{{{t = (-32 +- sqrt( 15936))/32 }}}


{{{t = (-32 +- 126.24)/32 }}}

solution (you need only positive solution)

{{{t = (-32 +126.24)/32 }}}

{{{t = (94.2)/32 }}}

{{{t = 2.9 }}}

so, your answer is:

D. {{{2.9sec}}}