1) If someone one handed in a purse, please put it in the lost and found drawer.
2) I handed in my assingment to the TA.
3) She handed the egg to the king. (this line is from a story "the king's egg")
In sentence no.1 & 2 there are "in" after the words "handed" but in sentence no.3 there isn't any "in". Please explain when is it necessary to use "in".
To hand in means to submit; present for acceptance; e.g., She handed in her term paper.
To hand means to give with one's hand.
If someone hands in a purse, please put it ...