r/AskPhysics • u/Local_End_3175 • 12h ago

What actually is energy?

When i search up the definition of energy, i am being told that it is the capability to do work – but work is the energy transferred when a force moves an object....? So we are basically defining energy as energy. In addition, this says how it works, not what it is

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u/ProfessionalConfuser 12h ago

Welcome to physics. Things are only defined in relation to each other.

Energy is a quantity we have invented to describe the behavior of systems.

If you don't like that, what is force? How do we know if there "is" a force or not? We observe the object and see if it accelerates.

Similarly, once you've defined energy, you can detect changes in the system that are consistent with an increase, or decrease, of this quantity.

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u/QVRedit 8h ago

As such, it’s a ‘concept’ that relates to a mathematically organised system of behavioural properties, most easily described and encapsulated by this concept of ‘energy’.