A common English grammar rule says that sentences cannot end with a preposition. This rule was derived from languages like Latin and French, in which it is grammatically impossible to put a preposition at the end of a sentence. Unfortunately, the rule is easy to break in English, and nowhere is this more evident than with phrasal verbs. As Winston Churchill supposedly said:
"This is the sort of English up with which I will not put."
Churchill's sarcastic statement uses a phrasal verb (English verbs that require more than one word to express their meanings), put up with, to make his point. The innocent phrasal verb appears to use prepositions, so purists insist that it must be split if it appears at the end of a sentence. As this quotation shows, splitting up the verb and its particles makes the sentence ridiculous.
Although some grammatical sticklers may disagree, it's generally accepted that a preposition is fine to end a sentence with.