In a balance pan, if you put 5 units weight on one side and 2 unit weight on the other, would not the 5 units come down as a result of gravity? Only for lifting a 5 unit weight you need to do give some input isn't it?
Can anyone explain what Feynman means when he is talking of a reversible machine in the chapter four of his lectures? What exactly is a reversible machine? Please explain this paragraph :
"If when we have lifted and lowered a lot of weights and restored the machine back to its original...