One of the most important laws in physics is the conservation of energy. Not only does energy have many significant forms, but also each form can be transformed into other forms. In this article, you will read about the concept of relativistic energy, total and rest energy forms.
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Concept of Relativistic Energy
Classical physics says that, in a system, the total amount of energy remains constant. Energy is still conserved relativistically, but to include the possibility of mass changing to energy, its definition changes accordingly. To conserve the energy in all inertial frames, relativistic energy is purposely defined in such a way that it will be conserved similarly, as is the case for relativistic momentum.
Total Energy and Rest Energy
The first hypothesis of relativity states that in all inertial frames, the laws of physics are the same. Einstein presented that relativistically the law of conservation of energy is valid, if energy is defined to include a relativistic factor.
Total Energy
Total energy E can be expressed as E = γmc2,
where m denotes the mass,
c denotes the speed of light,
and the velocity of the mass relative to an observer is denoted by v.
γ = 1/√1−(v2/c2)
There are many characteristics of the total energy E that can be taken into account. Some among them are how potential and kinetic energies are involved in E and how relativistic momentum is related to E. But at first, it should be noted that total energy is not zero at rest; rather, the object has rest energy because when v = 0, we have γ = 1.
Rest Energy
Rest energy is given by: E0 = mc2.
Einstein articulated this famous mass energy equation which for the first time exposed that the mass of an object at rest is related to its energy. For instance, the rest mass of an object increases if some energy is stored in it. This also suggests that to release energy, mass can be destroyed. The consequences of these equations regarding relativistic energy are so comprehensive that they were not totally recognized for some years of their publication by Einstein.
Kinetic and potential energy:
Stored Energy and Potential Energy
The input energy into an object eventually becomes part of its total energy, due to which the rest of the mass of the object increases. Suppose, by charging a battery, some energy is put into it in the form of charges, then after some time, the energy stored inside a battery becomes a part of its mass. This means that all potential and stored energy in a system becomes mass.
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Frequently Asked Questions (FAQs)
What is relativistic momentum?
Relativistic momentum can be defined as the product of relativistic factor γ and classical momentum p.
p = γmu
where,
m denotes the mass of the object which is at rest
u denotes the velocity of the object relative to an observer
and the relativistic factor if given by: γ=1/√1−(u2/c2)
State law of conservation of energy.
The law of conservation of energy signifies that a system always has the same amount of energy unless it’s added from the outside. Therefore, it states that energy can neither be destroyed nor be created; it can only be converted or transformed from one form to another.
What is total energy?
Total energy E can be expressed as E = γmc2,
where m denotes the mass,
c denotes the speed of light,
and the velocity of the mass relative to an observer is denoted by v.
γ = 1/√1−(v2/c2)
What is rest energy?
Rest energy is given by: E0 = mc2.
Einstein articulated this famous mass energy equation which for the first time exposed that the mass of an object at rest is related to its energy. For instance, the rest mass of an object increases if some energy is stored in it.
What is relativistic energy?
To conserve the energy in all inertial frames, relativistic energy is purposely defined in such a way that it will be conserved similarly, as is the case for relativistic momentum.
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