# Tag Info

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The classic gravitational measurement is the Cavendish Experiment, and the masses involved were a pair of 0.73 kg lead weights. So that forms an accessible reference. Other versions of the experiment may have used smaller weights, though.

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Gravitation effect on neutrons have been demonstrated. Bouncing neutrons To obtain neutrons with quantized gravitational energy states, the team used a technique first described in 2011, in which a nuclear reactor produces neutrons travelling at 2,200 metres per second. These are then slowed to less than 7 metres per second and cooled to just a ...

11

I found a 1988 paper by Mitrofanov et al which describes a Cavendish style experiment where the "big" mass was 706 mg - where Cavendish used balls of over 150 kg. The "small" mass ( the one on the torsion pendulum) was only 59 mg. This experiment was done to examine possible deviations of Newton's law at extremely short distances, and established a lower ...

9

When we pick standards for units it's important to pick standards that are as percisely defined as possible and measureable to very high precision in the lab. So for example the second is defined as 9192631770 times the period of the radiation emitted from a specific transition of the caesium atom. This is easily measured and indeed thousands of atomic ...

6

There are various reasons why water isn't a good basis for length measurements. In the long term, the most important is that water evaporates. To appreciate this, keep in mind that you can't just weigh out a kilogram of water and then somehow make a perfect cube container, then measure the sides. At the very least, dealing with the meniscus at the top would ...

3

The cause for neutrino oscillations is that the flavour eigenstates are not the same as the mass eigenstates. Therefore, once you know the flavour of a neutrino, i.e. whether it is a electron, muon, or tau neutrino, the mass is not well defined. And the other way around: Once you know the mass, the outcome of a flavour measuring experiment is uncertain. The ...

2

Short answer: no. Longer answer: In Newtonian gravity: definitely no. The gravitational attraction between two bodies depends only on their masses and separation. There is nothing else for the "amplifier" to couple to. In general relativity: practically speaking, no. For one thing in all "mundane" situations the predictions will be identical to those of ...

2

Mass is the scientific term. It's a measure of how much inertia a body has; that is, how hard it is to push around if it was sitting floating in space. It is a fundamental quantity and has units of kilogram. Weight is not really a scientific term. It's a common-speech term that means Force due to gravity. So strictly speaking, a weight should be in units of ...

2

I am not sure if Thompson ever determined the charge-to-mass ratio of a proton, but currently, the most precise measurements of the charge-to-mass ratio of a proton still use a magnetic field like Thompson, but rely on measuring (cyclotron) frequencies rather than deflection. As frequencies are the quantities that can be determined most accurate (see the ...

2

Why $m^2$ in front of $\phi^2$ and why is $m$ the mass? Fist of all, from dimensional analysis the prefactor to the $\phi^2$ term in the Lagrangian must have mass-dimension$^1$ $2$ in $3+1$ dimensions since the Lagrangian has mass-dimension $4$ and $\phi$ has mass-dimension $1$. This just tells us that we can write the term as $m^2\phi^2$ where $m$ is ...

2

Set up a device to measure the upward pull of a helium balloon. The upward pull in Newtons is the net buoyant force. The net buoyant force is the weight of the displaced air, with the weight of the helium and the weight of the balloon subtracted from it. Using the ideal gas law, calculate the weight of the displaced air and the weight of the helium. This ...

2

Well that depends. As always, you should be very careful with such reasoning as Due to the fact that gravity is related to the square of the distance should not the gravitational sum of every particle exceed the force when calculated by the center of mass. because this is a problematic statement. In general your (Newtonian) gravitational potential is ...

2

As stated above, the mass of the whole system (sugar + water) doesn't change. In addition, with "ideal" mixing, the total volume of the water plus the total volume of the sugar equals the total volume of the mixture. However, this is not a sure bet, and there are many cases of a volume of one material mixed with a different volume of water, and the total ...

1

Their paper is inconsistent. They filled in $\omega = 264$ with the other quantities in SI units, so ω should be expressed in rad/s (often written $\mathrm{s}^{-1}$). So they assumed ω was already in rad/s. If they say they assumed $\omega = 264~\mathrm{rpm}$, that's not consistent with the values they plugged in. Your value of 69696 is hard to decipher ...

1

Acceleration due to gravity remains roughly constant near the surface of the earth. Yes, $a = F/M$, but as mass increases, the force exerted by gravity increases too($F\ \alpha \ m1m2\over r^2$), keeping $F/M$ or $a$ roughly constant around the surface of the earth

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Here's how to intuitively understand that $a=g$. Take a metal ball having mass 1kg and drop it. Its downward acceleration is $9.8m/s^2$, right? Now take a second ball and drop it. Same thing, right? Now drop both at the same time. Same? Now connect them together (with a tiny drop of weld metal) into a single 2kg mass, and drop them. Do they suddenly slow ...

1

To give a qualitative answer, the equivalence of gravitational and inertial mass is not a coincidence. Mass has inertia and this resists its motion through space-time (we're moving into the future at the speed of light!). The resistance leads to a bending of space-time and it is this that we interpret as gravity. Sort of...

1

The mass doesn't change at all, it will be just the sum of the water mass and the mass Added, what happens is the change of density because the mixture, in general the molecules get closer to each other ( through the intermolecular forces) and, this way, the volume become lower to the same mass quantity, what increase the density by the equation $$\rho = ... 1 People have certainly measured the electron's charge and mass more than once in the last 100 years. See for example this table from the Particle Data Group, where you can find the constants you want to around 8 significant digits, much more than what was possible for Millikan. For comparison, Wikipedia claims that Millikan and Fletcher measured e to be ... 1 The textbook writer is referring to the concept of relativistic mass, which is the idea that accelerating a body tends to become harder and harder as its speed approaches the speed of light. This is sometimes thought of in terms of an increase in the object's mass as the speed increases. However, you should think of this as a deprecated concept that most ... 1 Keep in mind that the equation$$ E^2 = p^2c^2 + m^2c^4 $$is derived from the relations$$ \begin{align} E = \gamma mc^2,\qquad p = \gamma m v. \tag{1} \end{align} $$Therefore$$ p = E\frac{v}{c^2}.\tag{2} $$Although (1) is only defined for massive particles, it turns out that (2) remains valid when v=c, i.e. for massless particles. Indeed, we get$$ E= ...

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Sometimes people talk about "relativistic mass" which depends on your reference frame... this is perhaps what you're thinking of when you talk of your mass increasing as you approach the speed of light. However, more typically if a physicist says "mass" they mean the "invariant mass" or "rest mass" which is just your energy content (divided by the speed of ...

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