Could anyone explain me in simple words what is being said inthis topic from Feynman Lectures Vol.1 Chapter 4 topic 4-2Gravitational Potential Energy (great book and author btw)...pleaserefer to the book (pdf on net or a copy) to get what i'masking.
i don't understand after it starts talking about perpetual motionand lifting and lowering of weights.please explain in simplewords.
so i got confused at this point-
\"Consider weight-lifting machines—machines which have the propertythat
they lift one weight by lowering another. Let us also make ahypothesis: that
there is no such thing as perpetual motion with theseweight-lifting machines. (In
fact, that there is no perpetual motion at all is a generalstatement of the law of
conservation of energy.) We must be careful to define perpetualmotion. First,
let us do it for weight-lifting machines. If, when we have liftedand lowered a lot
of weights and restored the machine to the original condition, wefind that the
net result is to have lifted a weight, then we have a perpetualmotion machine
because we can use that lifted weight to run something else.\"
umm like how exactly weight lifting machine lift one weight bylowering another.and what does that line mean that no perpetualmotion at all is a general statement of the law of conservation ofenergy.im also confused by the last four lines and the whole topicthat follows...can't seem to visualize what is being said...so ifanyone can say the whole thing in this topic in simpler words orhelp me visualize it would be of great help.
im also a bit more confused by the next para-
\"
A very simple weight-lifting machine is shown in Fig. 4-1. Thismachine lifts
weights three units “strong.†We place three units on one balancepan, and one
unit on the other. However, in order to get it actually to work, wemust lift a
little weight off the left pan. On the other hand, we could lift aone-unit weight
by lowering the three-unit weight, if we cheat a little by liftinga little weight
off the other pan. Of course, we realize that with any actuallifting machine, we
must add a little extra to get it to run. This we disregard,temporarily. Ideal
machines, although they do not exist, do not require anythingextra. A machine
that we actually use can be, in a sense, almost reversible: thatis, if it will lift
the weight of three by lowering a weight of one, then it will alsolift nearly the
weight of one the same amount by lowering the weight of three.\"
why would you need to lift a little weight off the leftpan?wouldn't the machine lift the right side(with one unit) up assoon as you placed 3 units on the left side?also what does the lastfour lines here mean again?how will you lift a weight of 3 bylowering a weight of one?how can one weight on one side make 3weights on the other side go up?
