Free Fall Acceleration Problem

[chounx93]

Homework Statement

As a runaway scientific balloon ascends at 19.6 m/s, one of its instrument packages breaks free of a harness and free-falls. The figure below gives the vertical velocity of the package versus time, from before it breaks free to when it reaches the ground.

(a) What maximum height above the break-free point does it rise?
(b) How high is the break-free point above the ground?

Homework Equations

The Attempt at a Solution

i know part A is 19.6 m
i just can't seem to get the correct answer for part B

these are the variables that i have and i think i'll need
V0=0 m/s
t=6.0 s
a=-9.8 m/s/s
y-y0=?

i used this kinematic equation
y-y0=vt-1/2at^2
but the answer still isn't correct

 

[kuruman]

The package is at the break-free point at time t = 2 s and it is moving up. Can you figure out by looking at the graph at what later time it is at the same point, moving down?

 

[chounx93]

it's at the same point at t=4 s

 

[kuruman]

At t = 4 s the velocity is instantaneously zero. This mean maximum height.