How long until the mailbag reaches the ground?

[Mustapha13]

Homework Statement

The height of a helicopter above the ground is given by h = 3.00t3 , where h is in meters and t is in seconds. After 1.80 s, the helicopter releases a small mailbag. How long after its release does the mailbag reach the ground?

Homework Equations

a = delta v/ delta t= delta d/ delta t^2

The Attempt at a Solution

i keep getting 2.2 seconds which is wrong

 

[iRaid]

I think you have to find the velocity of the helicopter going up which will end up giving you the initial velocity of the mailbag. Also I think your equation you're using is incorrect, try the kinematics equations.