Learn Hardcore Russian: На работе мне полезно делать перерывчик каждый час. - At work it is useful for me to take a short break every hour.

на работе = at the workplace (location)
в работе is rare and usually means “in the process of some work / in terms of the work itself”, e.g. ошибка в работе “an error in the work.”

So to say “At work it’s helpful for me…”, you almost always use на работе.

What case is работе in, and why?

Работе is in the prepositional case (основная форма: работа).

The preposition на + prepositional case is used to describe being on/at some place or activity:

на работе – at work
на уроке – in class
на вечеринке – at a party

So на + работе (prepositional) answers “where?” – где?

What does мне полезно literally mean, and why is мне in the dative?

Literally, мне полезно means “(it is) beneficial to me.”

мне is dative: “to me / for me”
полезно is a predicative form meaning “beneficial / good (for health/benefit).”

Russian often uses an impersonal construction with the dative:

Мне холодно. – I am cold. (literally “it is cold to me”)
Тебе нужно отдохнуть. – You need to rest. (literally “it is necessary to you…”)
Мне полезно делать перерывчик. – It’s beneficial for me to take a small break.

So мне answers “to whom is it beneficial?”

What’s the difference between мне полезно and для меня полезно?

Both can translate as “good/beneficial for me,” but the nuance is different:

Мне полезно делать перерывчик… – natural, conversational, focuses on the state/benefit for the person; typical impersonal pattern (dative).
Для меня полезно делать перерывчик… – more formal or “external,” like evaluating something from my point of view or for my benefit.

In this sentence, мне полезно sounds more natural and colloquial.

Why is there no explicit subject, like это or я?

This is an impersonal sentence, which is very common in Russian.

Instead of saying Я должен делать перерывчик… (“I must…”)
Russian often says Мне полезно делать перерывчик… (“It is beneficial for me to…”).

There is no grammatical subject; the idea is:
(It is) beneficial for me to take a little break every hour at work.

The infinitive делать functions like the “subject” of the construction.

Why is it делать перерывчик, not a verb like перерываться or something else?

Russian very often uses делать + noun where English would use a single verb:

делать перерыв – to take a break
делать зарядку – to do exercises
делать паузу – to pause

So делать перерывчик is simply “to take a (little) break.”

There is no common verb like перерываться in this sense; перерваться exists but means more “to get interrupted” and is not used for “take a break.”

What’s the nuance of перерывчик compared to перерыв?

Перерывчик is a diminutive form of перерыв.

перерыв – a break (neutral)
перерывчик – a little break, a short break; often more casual, friendly, or “softer.”

Using перерывчик can imply:

it’s not a long break
the speaker is being informal/light-hearted, or just “softening” the statement.

You could say:

делать перерыв каждый час – perfectly correct and neutral
делать перерывчик каждый час – slightly more informal / “cute” / mild.

Why is делать in the imperfective aspect here?

Делать (imperfective) is used because the action is repeated or habitual:

делать перерывчик каждый час – to take a little break every hour, regularly.

Imperfective is used for:

repeated actions (habits)
general recommendations

A perfective form like сделать перерыв would refer to one specific break, not a repeated habit.

Can we change the word order, like Мне на работе полезно делать перерывчик каждый час or Делать перерывчик каждый час на работе мне полезно?

Yes, Russian word order is flexible, and those variants are possible:

Мне на работе полезно делать перерывчик каждый час.
Slightly more emphasis on “at work”: For me, at work, it’s helpful to…
Делать перерывчик каждый час на работе мне полезно.
Puts делать перерывчик каждый час на работе first, emphasizing the whole activity; sounds a bit more “formal” or “written,” or like a conclusion.

The original На работе мне полезно делать перерывчик каждый час is very natural and neutral in spoken language.

What case/structure is каждый час, and why not каждого часа?

Каждый час is accusative singular, used in a time expression meaning “every hour.”

Pattern:

каждый день – every day
каждую неделю – every week
каждый час – every hour

You don’t say каждого часа here; that would be genitive and doesn’t work with this “every X” time pattern. The fixed structure for “every [time period]” is каждый/каждую/каждое + accusative.