Motion Experiment - What's Accelerating? - The Box Or The Ruler? - levelheaded william

A simple accelerometer is a container with air and water because solids, liquids and gas will always displace under conditions of acceleration or when there's a force present. The water will always appear to move towards the back of the container and push the air towards the front. In other words, the air will always get pushed in the direction of acceleration 100% of the time.

When we're observing objects appear to move in a particular direction, vision alone is not a physical measurement of acceleration. For example, when I have a ruler going through a box, Whether I move the box or whether I move the ruler, the ruler is always going to appear to move because the camera is connected to the box. Unless we can observe it from the outside, the ruler will always appear to move. However, if I was to attach a simple accelerometer to the ruler, then we will know if it's the ruler moving or the reference frame, without having to observe it from the outside. Which ruler would you bet is the one accelerating, 1 or 2? So when we're talking about downwards acceleration, which bottle would you bet is the one accelerating, 1 or 2?

credit: levelheaded william original video: https://youtu.be/q6BP3BtnMvo?si=bGF8nltclTdchQvw