Homework help: Dropping a sand bag from a Hot Air Balloon

[Clockclocle]

Homework Statement

Suppose an air baloon keep raising with constant velocity v0, at time t=0 the sand bag attached to it drop at rest.

Relevant Equations

y=vo-1/2gt^2

In this situation should my free fall equation contain the v0 of the balloon or I should deny it. Because it seems to me that there is no outer force acts on the sandbag, so the scenario is just the same as I climb to the same height at time t=0 and drop the sandbag at rest.

 

[jbriggs444]

so the scenario is just the same as I climb to the same height at time t=0 and drop the sandbag at rest.

What if the balloon is rising at the speed of a rifle bullet? You are riding on the balloon holding the sandbag in your hand and let it go.

 

[Clockclocle]

I see the mistake, I thought that it gonna fall below me so it would be the same when I stand still. But in this case I keep moving with velocity v0.

 

[kuruman]

$\dots$ so the scenario is just the same as I climb to the same height at time t=0 and drop the sandbag at rest.

The acceleration is the same not the scenario. In the first case the velocity of the bag relative to the ground is the same as that of the balloon whilst in the second case it is zero. Different initial velocities mean different free fall trajectories.