Can we change the position of the object?

Question

I know google translate does the bare minimum job of translating a sentence into Japanese. The original sentence was, "I had to hit my head on the table." which was translated into "テーブルに頭を打たなければなりませんでした。" I tried changing the position of the object because it made more sense to me. The translated sentence I came up with was, "頭をテーブルに打たなければなりませんでした。" Can we use this instead?

Also, "打たなければなりませんでした。" seems a bit confusing. It translates to "I had to hit." but doesn't なければ mean "If not" and I don't know why "なりませんでした" was used.

Answer 1

Actually the meaning of the two Japanese sentences you wrote are the same. In simple sentences like this, the parts with the particle に、を、で are usually freely interchangeable, and do not affect the meaning. The meaning of リンゴをカバンに入れました and カバンにリンゴを入れました are exactly the same.

Note that for longer sentences with more complicated structures (for example when explaining reasons, order of actions, etc), changing the orders may also change the meaning of the sentences.

For なければなりませんでした please refer to the link provided in Chocolate's comment.