system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do pullies make objects seem lighter when they are lifted?
gpt
Pulleys are a way of transmitting work (Force x Distance).  The pulley systems effectively reduce the amount of force required to pull an object, but inversely proportionally increase the distance you need to pull.

Thus moving a 10kg a distance of 1m with a simple 2:1 pulley system would require pulling 2m of rope with a force of 5kg.

You can then increase this pulley advantage to lift very large loads, but very slowly.