# Tagged Questions

The property of an object that determines how much it responds to a force in Newtonian mechanics, and how much it interacts with gravity in the Newtonian framework. Mass also refers to the intrinsic energy of a particle in particle physics.

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### Must we test whether e.g. $A=B$ and $A=C$ implies $B=C$ by experiment?

Chaper 10, conservation of momentum in "The Feynman Lectures on Physics" in the chapter entitled, the authors write that Suppose we know from the foregoing experiment that two pieces of matter, ...
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### Using the product rule to expand Newton's Second Law?

Newton's second law says that $$F=\frac{\text{d}p}{\text{d}t},$$ where $F$ is the net force on a body. My question is, why can't the product rule be used to yield ...
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### Rotational dynamics equation for a variable mass system?

I'm searching for the formulation of Euler's rigid body dynamics in the case of a variable mass system. I'm reading the book Mechanics of Flight by Warren F. Phillips (2nd edition) and unfortunately ...
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### Why is the definition of mass and matter interlinked?

In my textbook the definition of matter and mass are: Matter: Any thing that occupies space and has mass . Mass: The amount of matter contained in a body. While defining "matter" we refer to ...
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### The relation between mass and speed

Massless particles (or luxons) have no (rest) mass ($m = 0$) and a speed equal to the speed of light ($v = c$). Massive particles (or bradyons) have mass ($m > 0$) and a speed lower than the speed ...
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### Is density of an element directly proportional to atomic number or atomic weight? [duplicate]

Is the density of an element directly proportional to any power/order of atomic weight or atomic number? I know very less, probably only highschool level physics, after which my brain has been ...
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### What happens to theoretical physics if a photon has non-zero mass?

I want to know the theoretical implication if photons have a non-zero mass. What happens to the Maxwell equations? What happens to QFT? If the photon have mass it can decade?
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### How many human cells will get affected at the prick of a pin? [closed]

Wikipedia states that there are 10^14 cells in a human body. My question is if I was to take a needle or a pin and pierce it just 2 mm in the body, how many cells will I be piercing?
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### If you double the mass of a moving object - is its kinetic energy quadrupled?

My colleagues and I were having a layman conversation about fuel consumption of boats vs planes etc. I was pointing out that according to the formula $$E_k = \frac{1}{2}mv^2$$ if you double the ...
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### How is mass conserved when a muon decays?

A small disclaimer: I am a layperson and not a formal student of physics so forgive any glaring stupidity betrayed in the nature of the question. A muon is supposed to always decay into an electron ...
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### Why is the momentum of a particle $\gamma mv$?

I am very new to relativity, and as I was going through Resnick & Halliday, I saw that momentum was no longer $mv$, rather $\gamma mv$. This was the proof: p = mv = m \frac{\delta x}{\delta ...
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### Bottle stableness optimization

A few days ago me and some friends played a game where you need to upset a bottle with a ball(flunkyball). Then a question occured: "How much water do we need to put into the bottle that its ...
133 views

### What's the significance of neutrino oscillations? [duplicate]

I read some about neutrino oscillations and flavour changing between three types of neutrinos. The question is, what is the significance of that observation? So far, we did not expect them to ...
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### Can we find actual rest mass of things on Earth

Earth moves around the Sun and the Sun moves around the galaxy and the galaxy moves with unknown speed and direction. We have speed so the mass of us all altered. Can we know the real rest mass? If ...
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### How the mass is conserved during continuous expansion?

If universe is continuously expanding doesn't it contradict the fact that mass is conserved? Because if mass is conserved so how is universe expanding?
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### How do scientists measure miniscule constants like the mass and charge and speed of an electron?

What can measure the extremely tiny mass of an electron? Is it through indirect means? The same goes for charge. The pull of a single electron must be infinitely small. And if one is to attempt to ...
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### Taking a derivative in a dynamic mass balance?

I'm practicing for a transport phenomena exam and I came across this question: A mothball with a diameter of 1.0 cm is hung (by a thread) in stationary air. Mothballs consist of pure naphthalene. ...
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### Feathers and Human Flight

In the case of Angels where they're supposed to have wings full of feathers and can fly. If we created a flight suit for humans made out of feathers, how big would the feathers have to be? If the ...
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### How can you explain objects of unequal masses falling at the same rate using GR?

Isn't gravity caused by the curvature of space-time, and the stronger it's curved the stronger the attraction? it makes more sense to me that if a heavier object is falling on earth it would fall ...
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### Are there any naturally occurring examples of photons without mass?

I read that a photon is said to have zero mass at zero velocity. Does this mean that they only exist in a state of probability until observed && interacting with some system? And then when ...
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### What did Tesla mean by “there is no energy in matter”?

I was reading "THE ETERNAL SOURCE OF ENERGY OF THE UNIVERSE, ORIGIN AND INTENSITY OF COSMIC RAYS" by Nikola Tesla, and he states: "There is no energy in matter except that absorbed from the ...
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### What is the use (/ meaning) of $F =ma$? [closed]

I have noticed that Euler's formula for force is useful with a couple of natural forces (at distance), like gravity, that can follow a body any length. If you consider the most common occurrences of ...
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### Can change in temperature cause a change in mass of an object?

If a gold bar is heated to say 200 degree Celsius then will it have the same mass at say 10 degree Celsius. Does energy has mass? If so then does this increased 'heat energy' cause an increase in the ...
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### Does negative mass reverse the arrow of time?

General relativity predicts that normal mass (positive mass) results in the curvature of spacetime which in return leads to gravitation. Since space and time are bonded together, any change on the ...
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### How to calculate the mass of a sun that is similar to our own

How would you calculate the mass of a sun that could host a habitable planet, with only given the values of the mass of our own sun. And the fact that it takes a specific amount of years for life to ...
1k views

### How did Newton find out gravity is proportional to the product of two masses? [duplicate]

I am going to ask a really stupid question here. It is a very well known fact that gravity is inversely proportional to the distance squared between two masses. I understand how he arrived at this ...
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### Units about weight

We know that weight is measured in Newtons. Since, $weight= mass\times gravity$. What will be the units of Newton? Will that be $N = kg\times g$ ? But we always measure our weight using the unit $kg$! ...
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### Connection between moment/torque and centre of gravity?

So I understand how moments work with regards to basic examples like pushing a door, in that the further you are away from the hinges of the door, the greater the moment, which is like a turning ...
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### Elements of particle mass

From what I can tell, it seems that particles have two kinds of mass, the mass inherent in a fundamental particle itself, or for composite particles, additional mass associated with the Higgs field. ...
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### Why are $W$ bosons massless above electroweak scale? [duplicate]

Because of the Higgs mechanism, one must replace the Higgs field $\phi$ with $\phi_0 + \phi_1$ where $\phi_0$ is the vacuum expectation value. As far as I understand, the $\phi_0$ gives the mass term ...
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### Where does the majority of the mass of the usual matter come from? [duplicate]

I apologize in advance to experts for the naivety of the question. It should be a duplicate but I didn't find any satifying question or answer about that. The proton is composed by two up quarks ...
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### Do we weigh more when standing near massive buildings?

I'm very new to the concepts of SR/GR and curvature of spacetime. My understanding is that the bending of spacetime is the causation of gravity, and that matter is the causation of the bending of ...
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### How black hole lose mass? [duplicate]

Even in empty space virtual particles can constantly pop in and out of existence in pairs, when 1 of the pair fall into the black hole while the other escape this is hawking radiation but black hole ...
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### Does scale invariance imply massless or continuous mass distribution?

$\newcommand{\ket}[1]{\lvert #1 \rangle}\newcommand{\bra}[1]{\langle #1 \rvert}\newcommand{\scp}[2]{\langle #1 \vert #2 \rangle}$ In his 2008 slides (PDF), Tzu-Chiang Yuan mentions the following on p. ...
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### Pressure, density, volume and mass in a room

Here's the question. A window in the room is open. The next day, the temperature of the room has increased, but the pressure of the air stayed the same. State and explain what has happened to ...
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### Why do non-accelerating objects exert force on each other?

The equation for force is $\vec{F} = m\vec{a}$, where $\vec{a}$ is acceleration. Acceleration is a change in velocity. However, if an object with constant velocity (i.e. 0 acceleration) hits another ...
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### How would an atom behave (in terms of atomic particles) if the electrons were much heavier than the nucleus?

In other words, does the mass of electrically charged particles affect the electromagnetic forces that operate between them ? Is the electrons revolving around the nucleus simply a consequence of the ...
670 views

### What is the difference between the mass of 100g and the weight of 1newton? [duplicate]

I was flicking through my physics textbook (as you do when you need to revise for a test that is going to decide your grade of the whole year), when a certain question caught my eye it read: Explain ...
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### Are all ground state protons the exact same mass and have the same number of elementary particles?

I have read that it is a misconception that a proton only has 3 quarks (2 up and one down). In reality, it seems there are many, many ("zillions" is the number I saw quoted) quarks in a proton. Do ...
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### Will 1 gram of matter moving at relativistic speeds completely annihilate a larger quantity of stationary antimatter?

This is a question about the relativistic mass concept which I am having trouble understanding, mainly because of the scenario below. Simple scenario: Suppose 1 gram of matter is accelerated to 99% ...
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### Kettlebell squats center of mass

I should, first of all, state that I have very limited knowledge of physics but as a fitness enthusiast the following question has puzzled me for a while. When I do squats on the gym holding a ...
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### A different interpretation of $E=mc^2$ but no idea what it might mean [closed]

I wanted $E=mc^2$ to look like an 'inverse square' sort of a formula. So this is what I derived: $E=mc^2$, so; $m=E/c^2$, assuming $E=E_1E_2$ (I am aware that when you decompose energy into two ...
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### How to calculate centre of mass

How do I find the centre of mass with given coordinates? For example if we have four objects with mass $m$ at coordinates of a square $(0,0,0),(0,0,a),(0,a,0),(0,a,a)$ or another example with eight ...
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### How do we measure mass?

How do you measure mass? Weight is easy using a scale, but we can't measure mass that way, because then mass would be different on every planet. I know there was a Veritasium video (here) on defining ...
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### How to measure the mass of Earth?

I was wondering how you can measure the mass of Earth. From what I find on the internet, people are using Newton's Laws. But how can you do that ? Newton's Laws are assumed to work because you know a ...
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### Center of mass of planar lamina

Suppose that $D$ is a closed region in $\mathbb R^2$ and let $\rho$ be a density function on $D$. Then, is it possible that the center of mass lies on the boundary of $D$? My intuition tells me that ...
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### How do we measure mass distribution in an object?

Given an object I want to know the mass distribution among different section. What are the inexpensive methods to know this ?
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### Is it true that all particles that have a speed less than the speed of light must also have mass?

I've previously learned that massive particles cannot achieve the speed of light. But recently I read that, concerning the gels that refract and bounce light within around enough that it can travel ...