Relative Velocity of Stone?

[kerol9904]

Homework Statement

A stone is dropped from a balloon at an altitude of 300 metres. How much time is required for the stone to reach Earth if:
(1) Balloon is ascending with a velocity of 5 m/s,
(2) Balloon is descending with a velocity of 5 m/s
(3) Balloon is stationary
Disregard air resistance.

Homework Equations

$x=x_0+v_0t-1/2gt^2$
$v=v_0-gt$

The Attempt at a Solution

I have no problem with question 3 but I fail to understand how the ascend or descend of balloon affect the stone. I assumed that it affected the initial velocity of the stone but I can't seem to find the formula for time.

 

[gneill]

What's the initial velocity of the stone when it's dropped from a moving platform? ("Dropped" means it's simply released).

 

[PaulDirac]

The question is about how to understand the initial velocity. When the balloon is moving upward (ascending) the object will have an upward initial velocity upon releasing, of course with the same magnitude as the balloon ascending. and vice versa in the case of downing.

 

[kerol9904]

Is it the same as the velocity of the platform itself?

 

[PaulDirac]

Is it the same as the velocity of the platform itself?

Yes, as I said above.