Book about two teenagers who find a physical constant changing device

Question

This story was a favorite of mine back in my childhood (perhaps early 2000s) and was released in the 1960s. I later found it again in the early 2010s, and identified it as the same story, but I can't recall the name from either of the two encounters, and the details I do remember don't agree well with each other.

From the 2000s, I remember that the story was about two (fairly modern, i.e. 20th century) teenagers who happened to stumble on a device of some sort that could change physical constants. (This is the only thing I remember from the 2000s story that I also remember from the 2010s story. I did decide that I recognized the story in the 2010s re-read, however, so I must've seen something else that was familiar.)
The device has detailed settings on it as to what exactly it can change, but the teenagers aren't especially well educated (having not reached university yet), so they have problems with understanding some of these settings. In particular, at one point near the beginning, one of the teenagers says (something along the lines of) "rotational period of Earth, 23 hours 56 minutes... why couldn't that thing just have said, there's 24 hours in a day?"
At one point near the end, one constant (temporarily) changed is the Earth's surface gravitational acceleration; specifically, it is changed to 1/4 of its normal value, to allow the protagonists to jump farther.
Also, there were pirates involved, somehow (this might have been the same scene as the above).

From the 2010s, I do not remember anything of the above aside from the general "two modern teenagers and a physical constant changer" setting. There are, however, some other things I do remember:
The device was supposed to come with an instruction manual, but a particularly unlucky accident led to the teenagers losing it very early on.
The ultimate setting of the device was to repeal the law of conservation of energy. Yes, I know that it's not any kind of physical constant. They have to use it eventually against some kind of evil guys (which might or might not have been the pirates from the previous list).
Oh, and the book was originally published sometime in the 1960s.

...Yeah, that should be all, I think.
You can treat both descriptions as referring to the same story in your search; I'm not 100% sure it is - in principle it could be two different stories - but given that I distinctly remember recognizing it as the same, I consider them being different fairly unlikely.

Answer 1

The story looks a lot like a Soviet young adult book Остров неопытных физиков (The island of inexperienced physicists) by Kirill Dombrovsky, which, to the best of my knowledge and google-fu, has never been translated to English. Below, I give my own translation for the passages.

was released in the 1960s

The edition I have was published in 1973, though it may not be the first edition of the book.

fairly modern, i.e. 20th century

The story appears to be set at least after 1960s.

-- А на Луну ты не хочешь полететь? -- спросил Алек Синичкин.
-- На Луну не хочу. Теперь это уже неинтересно, -- ответил Серёга.

-- Don't you want to fly to the Moon? -- Alek Sinichkin asked.
-- Not to the Moon. It's boring stuff, now, -- Seryoga replied.

Also,

Ну как же, самолёт изобретён? Радио изобретено? Атомная энергия освоена? Космические корабли летают? А что нам остаётся?

So what, they invented the airplane, the radio, harnessed the nuclear energy and launched spaceships! What yet do we have to do?

two teenagers

The main characters are four teenagers, Яша, Витя, Алек и Серёга (Yasha, Vitya, Alek and Seryoga), passing their summer time together.

who happened to stumble on a device of some sort that could change physical constants

-- Нужно сделать так, -- сказал Витя, -- мы придумаем такой прибор, который будет менять не все физические законы, а только некоторые и по определённым правилам.
-- Ты хочешь, чтобы он отменял трение? -- с некоторым сомнением спросил Алек.
-- Ну, пускай не совсем отменяет, а уменьшает раз в сто или двести...
-- В сто раз достаточно, -- сказал осторожный Алек.
-- Пускай отменяет закон Архимеда. Пользы от него никакой, а неприятностей много, -- посоветовал Яшка.
-- Нет, ребята, совсем начисто отменять физические законы не стоит, -- возразил Алек.
-- Ладно, -- согласился Яшка. -- Не хотите отменять совсем, давайте менять плотность воды... А что ещё?
-- Отменим скорость света!
-- Скорость звука!
-- Закон инерции!

-- That's what we do, -- Vitya said, -- we'll make a device that will change the laws of physics, not all of them, but some of them and within a certain set of rules.
-- Do you want it to cancel friction? -- Alek asked with a pinch of salt.
-- Well, not cancel, just make it a hundred or two hundred times smaller...
-- A hundred will do, -- Alek said cautiously.
-- Let it cancel Archimedes' law. No use of it, just troubles, -- Yasha suggested.
-- Wait, folks, it's not a good idea to cancel laws of physics altogether, -- Alek disagreed.
-- OK, -- Yasha agreed. -- If you don't want to cancel it, let's change the water density... What else?
-- Cancel the speed of light!
-- The speed of sound!
-- The law of inertia!

Also, some editions feature a magician that brings the device to the children, instead of children making the device out of thin air.

The device was supposed to come with an instruction manual, but a particularly unlucky accident led to the teenagers losing it very early on.

After they turn the friction off, guess what happens.

Витя пробовал застегнуть крышку футляра, ставшую такой же скользкой, как и всё. При этом он нечаянно выпустил из рук инструкцию. Эта тоненькая тетрадочка легко скользнула по траве и полетела дальше и дальше, к самой воде.

Vitya was trying to fasten the cover lid, which was as slippery as everything around, when he dropped the manual. The thin notebook glided on the grass and flew on and on, to the very brink of the water.

"rotational period of Earth, 23 hours 56 minutes... why couldn't that thing just have said, there's 24 hours in a day?"

Exactly.

Витька стал читать надписи подряд, одну за другой.
-- "Период суточного вращения Земли 23 часа 56 минут 4 секунды".
-- Почему это физики всегда самые простые вещи затуманивают? -- Яшка не любил физику и относился к ней с предубеждением. -- Ведь можно было сказать просто, по-человечески: сутки равны 24 часам, а они разводят канитель -- "период суточного вращения".

Vitya was reading the button labels, one by one.
-- "Earth daily rotation period is 23 hours 56 minutes 4 seconds".
-- Why do those physicists make the simple things so obscure? -- Yasha disliked physics and held a prejudice against it. -- You could say, in plain English: a day is 24 hours, and they make such a fuss with their "rotation periods".

one constant (temporarily) changed is the Earth's surface gravitational acceleration; specifically, it is changed to 1/4 of its normal value

-- Ребята, я тут нашёл одну подходящую кнопку: уменьшение земного ускорения в четыре раза.

-- Folks, I've found a neat button: makes gravity acceleration four times smaller.

to allow the protagonists to jump farther

Яшка попробовал ещё раз осторожно подпрыгнуть на месте. Он хотел подпрыгнуть совсем немножко, но взлетел почти на метр над палубой.

Yasha took another cautious jump. He wanted to jump a little bit, but sprang a meter up from the deck.

No pirates as far as I can see, but the characters explored a sunken ship with some treasures.

The ultimate setting of the device was to repeal the law of conservation of energy.

-- Как вы мне докажете, что закон сохранения перестал действовать? -- опять повторил Иенсен.
Глыба, которая весила, может быть, сотни тонн, от удара маленького булыжника сорвалась с места и, выворачивая песок и камни, сталкиваясь с другими скалами, покатилась по берегу.

-- How would you prove that the law of conservation works no more? -- Jensen inquired again.
A block that might have weighed hundreds of tons, was hit by a small cobble, took off and rolled along the beach, wreching sand and stones and hitting other rocks.

They have to use it eventually against some kind of evil guys

Jensen, an unlucky merchant who happened to travel with the protagonists, dreams of using their device for personal gain and steals it.