Questions tagged [conventions]
A convention is a set of agreed, stipulated, or generally accepted norms. It typically helps common efficiency or understanding but is not required, as opposed to a strict standard or protocol.
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Is gravitational potential energy of body by $mgh$ negative? [closed]
Consider a 15kg object at 1m from earth ground level,
is P.E = 15kg * 9.8m/s^2 * 1m = 147J
or P.E = -Gm1m2/r^2 * h = -9.8 * 15kg * 1m= -147J
after browsing for a while on debate of potential energy's ...
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How Can there be a Gravitational Potential when there is NO Gravitational Field? [closed]
How does it make any logic that there exist a potential when there is no net field
for example when we have a Hollow Sphere with mass we can find out the the gravitational *potential inside the sphere ...
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What's the difference? $\nabla_\mu e_\nu=\Gamma_{\mu \nu}^\rho e_\rho~\text{ and }~\partial_\mu e_\nu=\Gamma_{\mu \nu}^\rho e_\rho~?$
What's the difference? $$\nabla_\mu e_\nu=\Gamma_{\mu \nu}^\rho e_\rho~\text{ and }~\partial_\mu e_\nu=\Gamma_{\mu \nu}^\rho e_\rho~?$$
In John Dirk Walecka's book 'Introduction to General Relativity',...
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Why is work done by force $+mgh$ in the situation of throwing something up?
If there is a particle at point A(at rest) and a force moves it to point B(Above point A vertically)(final velocity = 0 at this point), the work done by gravity is $-mgh$. This I understand as the ...
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Significant figures when product is more by a factor of 10
A rectangular plate has a length of 21.3 cm and a width of 9.8 cm. Calculate the area of the plate.
A straightforward question, which you multiply and arrive at 208.74 cm2. Taking significant figures ...
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$CP$-transformation for fermionic bilinears
I am trying to derive the transformation of the fermionic bilinear $\bar{\psi}\psi$ under $CP$ transformation.
I know that $P$ acts as:
$$\psi(t, \vec{x}) \xrightarrow{P} \gamma^0 \psi(t, -\vec{x})$$
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Equation for real/complex $\phi^4$ theory
On wikipedia (see this link), the Lagrangians of the $\phi^4$ equation for real AND complex scalar fields are given. One may derive the Klein-Gordon equation by inserting into the Euler-Lagrange-...
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Why did we choose Coulomb's constant $k$ as $9\cdot10^9 \rm Nm^2/C^2$ while define unit of charge instead of any other number?
I understand that while defining charge, Coulomb had to choose any arbitrary value of $k$ to describe unit of charge. But, why did we chose $9\cdot10^9 \rm Nm^2/C^2$ as the value of $k$, but not any ...
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Sign conventions for the Lagrangian from the EM Lagrangian density
In Chapter 13.6 of the 3rd edition of Goldstein's Classical Mechanics, Goldstein proposes the Lagrangian density of the electromagnetic field as:
$$\mathcal{L} = -\frac{F_{\lambda \rho} F^{\lambda \...
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Is the gravitational potential energy of an object on the ground 0? [duplicate]
In class, we were reviewing kinetic and potential energy and my teacher claimed that on the ground, objects have potential energy. However, as they cannot fall further, isn't their gravitational ...
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Physical Quantities Sign Convention
I see that almost all physical quantities carry signs. But the confusion I have is what they really mean.
Does negative velocity mean decreasing velocity or velocity in the opposite direction?
Does ...
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What is the key difference between SI and MKS units?
In MKS as well SI system, the length, mass and time are measured in the units meter, kilogram and second, respectively. Then how the SI units are different from MKS units? What are the key ...
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Does the exponential representation of Dirac delta function depend on choice of Fourier convention?
Is it always true that
$$\delta(\omega) = \frac{1}{2\pi}\int_{-\infty}^{+\infty} e^{i \omega t} dt , $$
regardless of your Fourier convention?
For example, if I choose to use the Fourier convention ...
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Are zeros to the right really significant? [duplicate]
In one of YouTube lectures about significant digits I saw this:
I was completely shocked. Both scientific notation numbers when converted to integer would represent same quantity of $1200 \text{kg}$ ...
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Can a positive charge have a negative potential?
I'm studying about electrostatic potential due to a point charge and was wondering - can a positively charged point have negative electrostatic potential?
V=Kq/r for a positive point charge.
Assume B ...
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