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This microwave burrito advertises energy in units of kJ
(lemmy.world)
Recently got some burritos from a food bank and while looking for cooking directions I found this nutrition chart. Never seen a food product use anything other than calories for energy, thought it was interesting.
Whatever kind of energy was kept in mind as a unit was developed, all units of energy "are a measure" of the same thing: energy. And also work because that's actually just energy. They're just different sized units like cm vs inches or °F vs °C.
A fathom was designed to measure how deep water is, but nothing is stopping me from saying that a football field is 50 fathoms long. A calorie was designed to measure heat, but nothing stops me from saying it takes about 5 calories of work to compress a bike spring.
The reason we have the SI is that once you understand how all the different units for one quantity interact, and how they're related to the units for another quantity, we may as well just make them interact simply and stick to one unit for each quantity to reduce confusion.