system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do vehicles make those pinging and popping sounds when you turn them off after driving for a while?
gpt
Vehicles have lots of moving and tight-fitting parts, those parts heat up (expand) due to friction as you drive. When you stop and turn the car off, parts cool (at different rates due to differing materials and such). As they cool they shrink again, the popping happens when two parts snug against each other cool and reach a point where the static friction points (the specific points where the parts touch) slide past each other, creating sound.