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### Does inertia increase with speed? [duplicate]

I have heard that when the speed of the object increase, the mass of the object also increase. (Why does an object with higher speed gain more (relativistic) mass?) So inertia which is related to ...
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### What's the deal with Relativistic Mass? [duplicate]

So I have taken a first course in Special Relativity and the Relativistic Mass is defined as: $$m = \frac{m_o}{\sqrt{1 - v^2/c^2}}.$$ Now, when this was introduced in the course, it was introduced as ...
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### Is Feynman right? Does mass change with speed? [duplicate]

In chapter one of Feynman's famous Lectures on Physics, he writes the following. Mass is found to increase with velocity, but appreciable increases require velocities near that of light. A true law ...
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### When talking about atomic mass, how is $E=mc^2$ factored in? [duplicate]

When talking about atomic mass in the periodic table of elements, is this number the mass of the element at rest? If I understand correctly, the (relativistic) mass of an element will increase as the ...
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(This is a quick one) Suppose Im standing still (in my perspective) and a hoverboard is flying at $0.8c$ w.r.t me. I see that the ball (red) is moving at $0.8c$. I measured earlier that the ball is $... • 1,305 0 votes 1 answer 124 views ### Questions on Mass [duplicate] In my eyes, mass is a property of "matter" (I suppose) that indicates how an object reacts (accelerates) to an applied force. In special relativity lectures, if I recall correctly:$F=γ^4m_0a$So ... 0 votes 1 answer 77 views ### When a particle keeps "accelerating" near the speed of light, is the energy gained expressed in linearly gained impulse, or relativistic mass? [duplicate] When a particle keeps "accelerating" near the speed of light, is the energy gained expressed in linearly gained impulse, or relativistic mass? • 11 -1 votes 1 answer 310 views ### Where does the extra mass come from if an object approches speed of light? [duplicate] According to scientists, if an object approaches the speed of light, a stage is reached where the object's speed is responsible for the increase in mass of the object. Beyond that stage, all the ... • 25 0 votes 0 answers 61 views ### For Einstein's equation$E= mc^2\$ is it energy that increases or mass as the velocity increases? [duplicate]

I will be surprised if no one asked this before and I would be happy if it is answered already although I haven't located it just yet! From Einstein's original paper "Does The Inertia of a Body ...
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### Is the "mass means rest mass" school of thought within relativity theory still "Einstein's theory of relativity"? [duplicate]

Is the "mass means rest mass" (MMRM) school of thought within relativity theory still "Einstein's theory of relativity"? I have read that both MMRM and "mass depends on ...
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### Is mass relative? [duplicate]

Since time is relative to the observer's velocity, does that mean that velocities are also relative, since the same distance is covered in a different time, depending on your reference frame? If ...
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### Definition of mass in agreement with relativity [duplicate]

Generally, the mass of a body is defined as the amount of matter contained in it. But we also know from relativity that "mass of a body increases as it approaches the speed of light". Going by the old ...
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### Speeding up mass to the speed of light [duplicate]

Suppose you have mass of 1kg as you start to move it at a speed which is 90% of the speed of light then what will happen to that mass? Will it increase?
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### Mass of a free falling object [duplicate]

What does General Theory say about the mass change of a freely falling object in a gravitational field? That is, does its mass change as the velocity increases? And, similarly, does the mass of an ...
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