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25 votes
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Would you run faster on Mars?

The speed of walking and running depend on pendulum-like motion of the legs. If you walk at different speeds the power used varies, and has a minimum roughly corresponding to the free pendulum motion ...
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15 votes

Why relativistic mass of a body increases with its speed?

Let's rewrite this using $E=mc^2$ to show how the energy increases with velocity \begin{equation} E = m c^2 = \frac{m_0 c^2}{\sqrt{1-\frac{v^2}{c^2}}} \end{equation} Hopefully it is intuitive that the ...
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12 votes

Would you run faster on Mars?

Buoyancy is not what slows the motion of astronauts on the Moon. Buoyancy requires some heavier-than-you liquid to surround you (in order to impede you significantly). When vacuum surrounds you there'...
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7 votes

Why relativistic mass of a body increases with its speed?

I suggest you think of it in the following way... Newton's laws tell us that when you apply a force to an object, the resulting acceleration is inversely proportional to the mass of the object. So you ...
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6 votes

Would you run faster on Mars?

You question is interesting but perhaps a bit ill-posed. Consider, for example, the difference between a 100-m sprinter and a miler. The sprinter will lean as far forwards as possible so as to ...
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6 votes

Would you run faster on Mars?

Summary All else being equal, runners on Earth will accelerate harder up front, but runners on Mars will have higher top speeds. As such, longer runs will favor Mars, while shorter runs will favor ...
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  • 1,533
5 votes

Would you run faster on Mars?

This is a partial answer. Anyone who has run on an Alter-G treadmill will tell you that it is much easier to run at a given speed when your weight is artificially reduced in the way that Alter-G's do. ...
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  • 358
4 votes

Abraham-Lorentz force/electromagnetic mass/relativistic mass

First, the concept of relativistic mass has been discarded by the scientific community for decades now. Einstein wrote against using the concept back in 1948. Okun was particularly strong against the ...
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4 votes
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How does massless particles arise in string theory when it starts with the assumption that all strings are composed of massive little pieces?

Susskind corrects himself at 1:00:08 where he says that the "mass density" coefficient in front of the $\dot{X}^2$ term is a non-relativistic analogue; it is not actually a mass-density of ...
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3 votes

Why relativistic mass of a body increases with its speed?

Special relativity was originally proposed by Albert Einstein in a paper published on 26 September 1905 titled "On the Electrodynamics of Moving Bodies". The incompatibility of Newtonian ...
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3 votes
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Rigorous treatment for continuous mass systems

In discrete case we sum over particles, in continuous case we integrate over some space, physical or coordinate. When calculating e.g. coordinates of center of mass of some continuous body, summation ...
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2 votes
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Is gravity a direct result of Lorentz Contraction?

No. Special relativity on its own doesn't imply general relativity. It's not enough to have some invariance principles; you need to "turn on" mass-energy gravitating by specifying how they ...
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2 votes
Accepted

Why relativistic mass of a body increases with its speed?

I mean, "why" is a fun question because you're eventually destined to just get an "because the universe says so" answer, but I'll try and give the shortest, most intuitive ...
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  • 282
2 votes

How does massless particles arise in string theory when it starts with the assumption that all strings are composed of massive little pieces?

Here is a somewhat hand waving explanation that I think is appropriate given the nature of the question. The equations for the positions of the little masses along the string is essentially a wave ...
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  • 7,521
2 votes

Extension in Massive Springs under gravity

The trick is to evaluate the load situation of a slice of lenght $\Delta h$. As it is at rest, the downward force at the bottom of the slice $(F_h)$, plus the weight of the slice must be equal to the ...
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1 vote

What is the general dependence of volume change from mass change due to general relativity?

That means ΔV increases linearly with M. Now, I'm wondering whether this is valid in general or only regarding the earth? Is that ("ΔV increases linearily with M") an inference out of ...
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1 vote

Why does Newton's second law involve mass?

Newton's second law states that the force experienced by a body is vectorially equal to the rate of change of its momentum which is defined as mv. For a fixed mass, this rate reduces to the familiar ...
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1 vote

Nuclear fusion mass defect and energy production

This answer and the accompanying discussion may be helpful to you https://physics.stackexchange.com/a/667132/313823 It is really no different from a chemical reaction like $$H+OH \longrightarrow H_2O ...
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1 vote
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Kinetic energy of quarks and mass of proton

I assume the energy carried by the gluons is referring to the binding energy of the three quarks by the strong force. It is more complicated than this. See how the strong interaction is figuratively ...
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1 vote

Fusion energy origin

The helium nucleus (for instance) has 2 protons and no neutrons-the mass remains the same, so why did the mass defect occur? Helium nucleus contains two protons and one or two neutrons (depending on ...
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  • 37.4k
1 vote

Abraham-Lorentz force/electromagnetic mass/relativistic mass

If a body is un charged, how do we know that the same rules apply? As for a neutral object, we cannot test whether or not maxwells equations apply. We can, and all experiments are consistent with ...
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1 vote

On what ground do you multiply $m$ with $v$ in the momentum equation $p=mv$?

Strictly speaking, a definition doesn’t need justification. However, some definitions are useful and important, and it is relatively easy to show why they are useful. In the case of momentum, ...
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