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Here's Figure 4.1:

Figure 4.1

And an excerpt from the Feynman Lectures on Physics Chapter 4.2:

A very simple weight-lifting is shown in Fig. 4-1. This machine lifts three units "strong". We place three units on one balance pan, and one unit on the other. However, in order to get it actually to work, we must lift a little weight off the left pan. On the other hand, we could lift a one-unit weight by lowering the three-unit weight, if we cheat a little by lifting a little weight off the other pan. Of course, we realize that with any actual lifting machine, we must add a little extra to get it to run.

It seems to me that Feynman is ascribing two different meanings to the verb "lift". One is getting the boxes in an upper position relative to the ground, and the other is removing weight from one of the pans of the machine (when "lift" is used in conjunction with "off").

Is my assessment correct?

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    Feynman's "we must lift a little weight" means "we must remove a little weight". Nov 22, 2020 at 14:43
  • So the word "lift" is used to describe two different physical actions in this paragraph, no? Nov 22, 2020 at 14:45
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    Yes, that's right. Feynman is trying to explain something in everyday language. Nov 22, 2020 at 14:46
  • Thanks, Weather. Your comments make for a perfectly legitimate answer - I would award it as the solution if you posted it. Nov 22, 2020 at 14:48
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    If you think that the writer uses the same word for "different physical actions", then you are missing that lift off is different from lift. Nov 22, 2020 at 14:53

5 Answers 5

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The Lexico dictionary shows two meanings for

lift
VERB

1 Raise to a higher position or level.

2 Pick up and move to a different position.

It is unfortunate that Feynman has created confusion in OP when trying to explain something in everyday language.

As pointed out by @YosefBaskin, the author has used lift off, but it would have been clearer to say remove.

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    @YosefBaskin is correct, but Feynman's wording is still confusing. "lift" and "lift off" share a common denominator, that is, "lift". Nov 22, 2020 at 14:55
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    Personally, I don't find this text confusing. Furthermore, during the 20 years I've been editing The Feynman Lectures on Physics, through which I've received thousands of reports of actual or purported errata, no one has ever complained to me that this text is confusing. Nov 23, 2020 at 20:22
  • @MichaelA.Gottlieb not to you: but here the OP states he was confused. Nov 23, 2020 at 20:25
  • @WeatherVane. Yes, the OP was confused, but I was responding to what you wrote, that "Feynman has created confusion," with which I disagree. I don't think the text is confusing, and as previously mentioned, no one has complained to me about it. I think the OP is confused for other reasons. Nov 23, 2020 at 21:13
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    @MichaelA.Gottlieb this is splitting hairs, really, and is no reflection on your editing. If Feynman wrote (or spoke) those words, then they were his creation. Obviously he did not intend to cause confusion, but confusion there is, whether OP is the only confused person, or not. OP's comment links to other sources of confusion. Nov 23, 2020 at 21:35
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The verb "to lift" is combined with "off" to form a phrasal verb meaning "to get off the ground" when talking of rockets or aircraft. This is not the verb in question, of course, and the particle (adverb) is not separable; here the basic meaning of "to lift" (Raise to a higher position or level (ref.) disappears because of the adverb "off" that has been added. (Remark: this is mentioned so as to provide an overview of how the particle "off" can be used with a verb or in connection with a verb.)

"Off", as an adverb, can be used with verbs to mean "so as to be removed or separated" (Lexico, 2); the meaning of "lift" is the regular one but "off" adds a precision. In this usage the particle is separable, or rather, so as not to use the vocabulary reserved for phrasal verbs, it doesn't have to be placed directly after the verb and pronouns can be found there instead. This is still not the usage found in the paragraph.

‘If they must graze on the hillside, the reservoir must be fenced off to keep them at a safe distance.’
‘It matters not whether the brandy ignites, but the alcohol must be boiled off.’
‘The second-floor room was sealed off as officers carried out a detailed search.’

(ref. 1) He lifted it off and standing in a holder underneath were twelve wooden boxes.

(ref. 2) When she sidestepped, it made it easier for him to undo the cinch on her saddle. He lifted it off with one hand ...
(same remark as precedingly)

In "we must lift a little weight off the left pan" and in "by lifting a little weight off the other pan", the word "off" is a preposition and has nothing to do with the verb or if it does it is a matter of purely semantic connection (You can lift a dish off a table but you can't think a dish off it); "off" is used to say that something has been removed or separated from something (in these instances, from the pan). (Lexico, preposition 3)

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If I lift Thing X off of Thing Y I remove it from Thing Y.

And, yes, "lift" has two meanings: (1) to raise something higher, and (2) to apply an upward force on something, whether it moves or not.

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It seems to me that to lift is

transitive: I lift the weight - OED 1. a. To raise [something] into the air from the ground, or to a higher position; to elevate, heave, hoist

intransitive: The weight lifts - OED 3. intransitive for reflexive (also with up). (a) To rise. Said esp. of a vessel riding on the waves, occasionally of the waves themselves. Also in quasi-passive sense (e.g. of a window): To admit of being raised.

Off is either an adverb ~ away or a preposition ~ from

The lectures are written verbatim with some, but not a lot, of correction. To those present, there would be no confusion, and I found none reading it.

I can see no need to change anything.

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  • The lecture may not be logically flawed, but it can disorient some readers, especially non-native English speakers. The solution is simple: use an alternative wording for "lift off". Nov 22, 2020 at 17:28
  • @PaulRazvanBerg Feynman's lectures were not intended as language learning exercises: they were addressed to some of the best young minds of the time, including non-native speakers, and were to teach them Physics. Your suggestion of rewriting them, is akin to suggesting all pre-20th century written works be translated into current English. The Master shows the way: the student makes the effort. :)
    – Greybeard
    Nov 22, 2020 at 17:43
  • Feynman being a brilliant teacher does not rule out the possibility that this specific explanation has been poorly written. Please refer to 1, 2 and 3 for a preview of the many confusions caused by this chapter. Nov 22, 2020 at 18:00
  • And the idea that my suggestion about this specific chapter is akin to re-writing all of the pre-20th century works is a non sequitur. Nov 22, 2020 at 18:05
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lift - you just take something
lift off - you remove

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    "Lift off" is what comes after "... three, two, one".
    – Hot Licks
    Nov 22, 2020 at 17:21

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