When Does the Package Reach the Ground?

[sprinter08]

Homework Statement

A helicopter is ascending vertically with a speed of 5.5m/s. At a height of 100m above the Earth, a package is dropped from a window. How much time does it take the package to reach the ground?

Homework Equations

delta y = Vot + 1/2at^2

The Attempt at a Solution

well I know that:
Vo= 5.5m/s
a=-9.8 m/s^2
delta y= -100m

I re-wrote the equation so that I would solve it using the the quadratic formula.
-5.5 + the square root of (5.5)^2 -4(-4.9)(100)/ 2(-4.9)
My teacher gave us the answer of t= 5.11s, but I can't figure out how he did it.

 

[Doc Al]

Here's a site with the full quadratic formula: http://mathworld.wolfram.com/QuadraticFormula.html" . Just plug in the numbers and you'll get 2 solutions. Only one will make sense for this problem.

 

[PhanthomJay]

Your equation is not quite correct it's -5.5 plus or minus the sq rt...etc. You will get 2 values for t...which is correct? (also, be sure to check all math).