system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does the seatbelt know that it's being pulled fast (crash) and stop extending but still extends when pulled slowly?
gpt
true eli5: imagine standing in a very small room. Relax your arms and turn slowly. Your arms will stay close to your body. Now turn fast. Your arms will move away from your body and hit the walls slowing you down.