Question 480853
h=0 when it reaches the terrace height on its way down

{{{ h= 16t^2 + 48t + 160}}}
{{{ 0= 16t^2 + 48t + 160}}}
{{{ 0= t^2 + 3t + 10}}}
solve using quadratic formula
{{{t = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
{{{a = 1}}}
{{{b = 3}}}
{{{c = 10}}}
{{{t = (-3 +- sqrt( 3^2-4*1*10 ))/(2*1) }}}
{{{t = (-3 +- sqrt( 9 - 40 ))/2 }}}
The square root is  negative which is absurd.
The equation should be 
{{{ h = -16^2 + 48t + 160}}}
{{{ 0 = -t^2 + 3t + 10}}}
a = -1,b = 3,c = 10
{{{t = (-3 +- sqrt( 3^2-4*(-1)*10 ))/(2*(-1)) }}}
{{{t = (-3 +- sqrt( 9 + 40 ))/-2 }}}
{{{t = (-3 + 7)/-2}}} (ignore negative number)
{{{t = (-3 -7)/-2}}}
t = 5
The object will hit the ground in 5 sec
m.ananth@hotmail.ca