system
Given the following post, respond as if you're commenting on Reddit:
human
Why does tapping on the edge of a stuck jar lid loosen it and make it easier to open?
gpt
It breaks some of the hardened salt (or sugar, or whatever crystalized substance) keeping the lid from turning. It doesn't work if the lid is stuck because of something viscous instead of hard; for those, a prolonged application of medium force works better than a very strong force of short duration.