[logophobia]

Zero acceleration only happens after an object has been falling for a long time (more then a few seconds) and the friction is in balance with gravity. Zero acceleration also happens when the laptop is just sitting on a table. Probably wouldn't be a good measure to stop the drive.

Initially, an object falling will accelerate with g=9.81m/s^2, after it reaches the ground it will de-accelerate to a speed of 0m/s in a couple of ms. You are confusing weightlessness/zero-g with no acceleration.

[Isamu]

I'm talking about the acceleration that the sensor is measuring. If you are holding it still, it measures 1g toward the ground.

If the drive is falling, certainly it is accelerating toward the ground but the sensor measures zero acceleration. This is the relative frame of reference.