Breakdown of Мы пользуемся этой большой ложкой и той маленькой вилкой.
и
and
мы
we
большой
big
маленький
small
Questions & Answers about Мы пользуемся этой большой ложкой и той маленькой вилкой.
Why are the spoon (ложкой) and fork (вилкой) in the Instrumental case here? Is it just because they are physical tools?
You are right that the bare Instrumental case is used to show the tool you use to do an action (like eating with a spoon). However, here there is a second, even stronger reason! The verb пользоваться (to use) strictly requires its object to be in the Instrumental case. Because of this verb, anything you use will take the Instrumental ending, even if it is not a physical tool (like using the internet or a service).
Why do the adjectives end in -ой (большой, маленькой)?
Because they must match the feminine nouns they describe, which are in the Instrumental case. Feminine singular adjectives take the -ой (or sometimes -ей) ending in the Instrumental. It can be tricky because this -ой ending looks exactly like the feminine Genitive, Dative, and Prepositional endings you've already learned, but here it is doing an Instrumental job!
Are этой (this) and той (that) also taking the Instrumental ending?
Yes! Just like the adjectives, feminine demonstrative pronouns reuse an ending you already know. The Instrumental form of эта is этой, and the Instrumental form of та is той. They perfectly rhyme and match with the adjectives and nouns that follow them.
Why does пользуемся end with the reflexive -ся suffix if we are just using a spoon, not doing something to ourselves?