Question 976217
{{{h = 320-16t^2}}}



{{{0 = 320-16t^2}}} Plug in {{{h = 0}}}



{{{16t^2 = 320}}} Add {{{16t^2}}} to both sides.



{{{t^2 = 320/16}}} Divide both sides by 16.



{{{t^2 = 20}}} 



{{{t = sqrt(20)}}} Apply the square root to both sides



{{{t = sqrt(4*5)}}}



{{{t = sqrt(4)*sqrt(5)}}}



{{{t = 2*sqrt(5)}}}



{{{t = 4.47213595499958}}} Use a calculator here



{{{t = 4.5}}} Round to the nearest tenth



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It will take approximately <font size = 5 color="red">4.5 seconds</font> for the object to fall 320 ft. This is ignoring air resistance.



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