Question 943272
Using feet and seconds,
{{{ h(t) = -16t^2 + v*t }}}
-----------------------
The time coordinate of the 
highest point is at:
{{{ -b / ( 2a ) }}} where
{{{ b = v }}}
{{{ a = -16 }}}
{{{ -b/(2a) = -v/(2*(-16)) }}}
{{{ -b/(2a) = v/32 }}}
{{{ v/32 = 4 }}}
{{{ v = 128 }}}
The ball was going 128 ft/sec when it
left the boy's hand
-------------------
Here's the plot:
{{{ graph( 400, 400, -2, 10, -50, 300, -16x^2 + 128x ) }}}
check:
{{{ h(4) = -16*4^2 + 128*4 }}}
{{{ h(4) = -256 + 512 }}}
{{{ h[4] = 256 }}}
Looks about right