Learn Dutch: Het verkeersbord kan morgen op de hoek worden geplaatst. - The traffic sign can be placed on the corner tomorrow.

Geplaatst does mean "placed," but to form the passive voice ("to be placed"), Dutch uses the helper verb worden. Because this sentence uses the modal verb kan (can), the rest of the verbs are pushed to the end of the sentence. There, the past participle (geplaatst) and the infinitive worden (to be) group together to mean "be placed."

Could I change the order at the end and say geplaatst worden instead of worden geplaatst?

Yes! When you have a past participle and an infinitive grouped together at the end of a clause, their order is usually flexible. Both worden geplaatst and geplaatst worden are completely correct and mean exactly the same thing.

Why does morgen come before op de hoek in the sentence?

This follows the standard Dutch word order rule often called Time-Manner-Place. Expressions of time, like morgen, almost always come before expressions of place, like op de hoek.

Why does the sentence use op de hoek? Would in de hoek work too?

When talking about an outside corner, like a street corner, Dutch uses op de hoek. If you used in de hoek, it would mean the inside corner of a room or enclosed space, which wouldn't make sense for a traffic sign.