Solving for Time: Dropping Package from Helicopter

[atbruick]

Homework Statement

A helicopter is ascending vertically with a speed of 5.83 m/s. At a height of 121 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground?

Homework Equations

Vfinal=Vinitial + at
or
Xfinal=Xinitial + Vinitial(t) + (1/2at)squared

The Attempt at a Solution

I tried putting in my answer from the first equation but it was wrong, and every time I try the second equation I get a negative answer which doesn't make sense.

 

[nick850]

negative time in physics doesn't really mean anything. all the negative means is that you put a negative -9.8 acceleration for gravity

the problem gives you this data:

d = 121m
vi = 5.83 m/s (initial velocity is 5.83 meters per second. yes it is negative since it's going down but we aren't going to worry about it)
a = 9.8m/s^2
t = ?

so you use this equation:
d= vi + 0.5at^2
121 = 5.83+.5*9.8*t^2
t = 4.8481 seconds

 

[atbruick]

My online homework say's that's not correct. I'm also confused on how you derived your equation?

 

[Arturo Andujo]

well i found out the velocity at the time of collision 1st with v^2 =vi^2 +2a(x-xi) to be 49.05 and then using the 1st equation i got the time to be 5.6 or 5.599

edit: if your homework was anything like mine then it was probably asking for that too and i found it easier to get that answer 1st