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I am translating a paper about a general physics question. I am not very familiar with physics other than the historical perspective and I am requesting some help with the grammar. I have a sentence that translates perfectly from the original Spanish as follows:

“At the moment of t1 at which both objects reach the ground, y1(t1)=y2(t1)=0.”

In English, a complete sentence requires a subject and a predicate. In the above sentence, the subject would be “y1(t1)”, which I guess I don´t have a problem with. My query is regarding the simple predicate, which in this case would be “=”. All of the English words in this sentence amount to prepositional phrases.

Is this standard use of language in scientific documents in English? Should I change the sentence to read something like, “The formula y1(t1)=y2(t1)=0 is satisfied at the moment…”?

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I think that the only problem with your sentence is "At the moment of t1". I would drop "of" and simply say "At the moment t1...". The rest of the sentence looks and sounds fine to me, but then I'm not a native speaker :) – Armen Ծիրունյան Dec 23 '12 at 21:53
The "=" in the equation can play the role of the verb, which means this translation is fine (except, as @Armen recommends, I'd drop the "of"). – Peter Shor Dec 23 '12 at 21:57
The symbol '=' in an equation is pronounced equals (always singular present) /'ikwəlz/. The whole equation is pronounced /'waywən əv 'tiwən 'ikwəlz 'waytu əv 'tiwən 'ikwəlz 'zɪro/. The subscripts should be printed sub-, however; i.e, y₁(t₁) = y₂(t₁) = 0. Oh, yes, and no of, as pointed out. – John Lawler Dec 23 '12 at 22:02
Also see “Four plus two equals six” (or “is equal to six” or “is six”)about how to read “4 + 2 = 6”. – jwpat7 Dec 23 '12 at 22:45
'At time t₁' would be more usual than 'at moment t₁'. – Edwin Ashworth Dec 23 '12 at 23:00
up vote 0 down vote accepted

I would rephrase it to...

At time t1 when both objects reach the ground [some equation].

Semantically, [some equation] is simply a statement, which could normally stand on its own as a complete sentence anyway. Substituting something simpler, such as "A=B", it's obvious that we could convert that to words ("A is equal to B"). There's no reason to suppose just because OP's form is a little more complex, it needs any additional text (such as "is true", or "is a satisfied equation").

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I think using moment is probably ill-advised, as @EdwinAshworth has commented. See ODO sense 3, bearing in mind that this is a physics question. – Andrew Leach Dec 23 '12 at 23:53
You are right. Edwin Ashworth pointed out that the correct word in this case is "time" and I confirmed on Google. – Turrialba Dec 24 '12 at 0:03
I agree with all three of you. I pussyfooted around trying to make the least change I thought was "necessary". I'll change it to reflect what I think we normally see in such contexts. I'll just mention that although I think most "wordsmiths" would probably demarcate when both objects reach the ground with commas, I have the feeling most "technical writers" wouldn't do this. I don't think the original (just one comma at the end) has much to commend it in a technical context. – FumbleFingers Dec 24 '12 at 2:46

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