system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is a 50lb dumbbell so easy to pick up, but a 50lb bag of salt feels like it weighs 100lbs?
gpt
There’s rigid weight and then there’s “dead” weight.

A solid mass like a dumbbell has a constant center of mass and you just have to lift from the center of mass.  It’s also designed to be grabbed.

A more gelatinous object is “dead” weight and will shift the center of mass as you move it, forcing you to continually attempt to adjust to the new center.  The more unstable the material is, the more pronounced this effect becomes.  Lifting a 50lb bag of liquid is almost impossible because it offers no easy grip points and wobbles everywhere.