Mailbag dropped from a helicopter at 20.8 m with initial velocity 31.2 m/s

[grewas8]

Homework Statement

The height of a helicopter above the ground is given by h = 2.60t3 , where h is in meters and t is in seconds. After 2.00 s, the helicopter releases a small mailbag. How long after its release does the mailbag reach the ground?

Homework Equations

yf=y(initial) + v*delta t

The Attempt at a Solution

h = 2.60 (8) = 20.8 (height at the bag is released)
y(initial)=0
v= 7.8t^2= 31.2 m/s
i dun understand if gravity would be used here and if it is can u just use the quadratic eqn

 

[learningphysics]

Everything you did looks good. Yes, you'll have to use the quadratic equation.

 

[learningphysics]

yf=y(initial) + v*delta t

this equation isn't right since velocity isn't constant... but you didn't use this equation.