In the English sentence, the preposition "with" conveys the idea of "by means of".

In the English sentence, the preposition "with" conveys the idea of "in the company of".

In Russian the idea of “by means of a fork” is expressed by the instrumental case of the noun "fork" without a preposition.

In Russian the idea of “by means of a fork” is expressed by a preposition and the noun "fork" in the instrumental case.