1. I learned that 'because' is different from 'since'. But, I can't distinguish the difference in meaning or in usage. How do you use these two conjunctions differently?
The conjunctions since, because, and as may be used at the beginning of a sentence, when the reason is already well known or when the reason is considered not as important as the main statement: As you're only staying a little while, we'd better eat now. Because puts a greater emphasis on the cause: Because she was witty and lively, she was often invited to be the keynote speaker.Because and for are both used to introduce reasons that justify a statement as distinct from giving a reason for it, though for is more literary in style: You must have forgotten to invite them, because they didn't turn up.He blushed, for he knew he had been caught out. For as a conjunction is never used at the beginning of a sentence. As can also be understood to mean "at the time that" as well as "because": As Luisa went back to work, Tony stayed home to take care of the baby. In this case, it is better to avoid ambiguity and use either because or while as appropriate. Avoid using being as in place of because in formal writing: They left for the game late, because [not being as] the car wouldn't start.
[Microsoft® Encarta® 2006. © 1993-2005 Microsoft Corporation.]
2. Hope someone to explain the meaning of the following sentence, please. I can't get the meaning of the 'pulling onto' below.
He used his car to block a tractor-trailer from pulling onto a highway.
pulling [out] onto a highway, in this context means to run uncontrollably out onto the highway from another street, he allowed a trailer to hit, or at least to be blocked by, his car.