Thursday, July 2, 2015

word choice - Article usage: "to the speed of 8 km…" vs "to a speed of 8 km…"


I have to take the TOFEL soon, and encountered a sentence from a textbook which made me think. In the case below, instead of using a as a preposition, is using the wrong?




Quote: To deliver a satellite into orbit, a rocket has to accelerate the satellite to the (originally it was “a”) speed of 8 kilometers a second more than 30 times than the speed of a jet aircraft.



I am wondering the text is using the preposition "the" when it is talking about the speed of a jet, but it is using the preposition a in succeeding case.


In this case, the succeeding paragraph is talking about the speed in general, so am I wrong?




I encountered another same thing. The phrase of the text is,



Light travels through a vacuum at a speed of nearly 3*108 m/sec



So a might be a winner with a slight edge.





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