Posted by emilia on Sunday, April 15, 2012 at 12:15pm.
a helicopter is ascending vertically with a speed of 5.20 m/s. at a height of 100 m above the Earth, a package is dropped from a window. how much time does it take for the package to reach the ground ? (hint: v0 for the package equals the speed of the helicopter). thank you !

intro. to physics  Elena, Sunday, April 15, 2012 at 1:06pm
h=v(o) •t +gt^2/2,
g•t^2 +2•v(o) •t 2•h•= 0,
9.8•t^2 +2•5.2 •t 2•100= 0,
t = {10.4 ±sqrt[(10.4)^2+4•9.8•200]}/2•9.8.
t = 4.01 s 
intro. to physics  Elena, Sunday, April 15, 2012 at 3:25pm
h=v(o) •t +gt^2/2,
g•t^2 +2•v(o) •t 2•h•= 0,
9.8•t^2 +2•5.2 •t 2•100= 0,
t = {10.4 ±sqrt[(10.4)^2+4•9.8•200]}/2•9.8.
t = 4.01 s