In the above diagram, assume that the level is solid and massless:
- In the left setup, both mass are fixed on the level. As we know, it is not a stable mechanical balance. For any tilt, the level will tilt more.
- In the right setup, both mass are hanged from a fixed location from the level. It is also the normal and old-fashioned setup for mechanical analytic balance. As we know, it is a stable mechanical balance. If one end is heavier than the other, the level will tilt to an angle and restore the balance.
But I can arrive at the above conclusion using mechanical analysis, e.g.:
- If the two ends are not balanced, at what angle the level will stop.
- For the above to happen, what is the range of the ability to restore balance at any tilted angle.