Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics
Linux Systems
Linux Systems
Power Users
Power Users
Tabletop RPGs
Tabletop RPGs
Community Proposals
Community Proposals
tag:snake search within a tag
answers:0 unanswered questions
user:xxxx search by author id
score:0.5 posts with 0.5+ score
"snake oil" exact phrase
votes:4 posts with 4+ votes
created:<1w created < 1 week ago
post_type:xxxx type of post
Search help
Notifications
Mark all as read See all your notifications »

Posts by celtschk‭

12 posts
81%
+7 −0
Q&A Unusual way to write spacetime coordinates/metric: Is there any downside?

In special relativity, spacetime coordinates are normally given as $$(ct, x, y, z) \tag{S}$$ with the metric being either $$g = \operatorname{diag}(-1,1,1,1) \tag{+}$$ or $$g = \operatorname{d...

1 answer  ·  posted 3y ago by celtschk‭  ·  last activity 3y ago by dmckee‭

80%
+6 −0
Q&A Would we need Alternating Current if superconducting wires existed?

The major advantage of AC is that is can be easily transformed to different voltages. This is important because current transport is most efficient if the currents are low (because the losses are p...

posted 3y ago by celtschk‭  ·  edited 3y ago by celtschk‭

Answer
80%
+6 −0
Q&A Should I always write units in equation no matter if it looks like variable?

In short: Yes. And there are standard ways to distinguish variables from units. Let me explain in detail. In physics, we deal with physical properties of objects and systems. Those quantities can ...

posted 2y ago by celtschk‭  ·  edited 2y ago by Canina‭

Answer
71%
+3 −0
Q&A What is inflation in cosmology?

Inflation in cosmology refers to a phase of the early universe where the universe expanded extremely fast. And the universe expanding quite literally means the space getting bigger. As you noticed...

posted 3y ago by celtschk‭

Answer
71%
+3 −0
Q&A What is the meaning that the universe is flat?

To understand this, it helps to look at a dimension less. Imagine, you're having a dispute with a flat-earther about whether the earth is a sphere or a flat plane. Moreover, there's a third person...

posted 2y ago by celtschk‭

Answer
71%
+3 −0
Q&A Why we can't find a particle accelerating unless there's some other particle accelerating somewhere else?

If you are accelerating while running on Earth, actually you are also accelerating Earth in the opposite direction. However for a given force, the acceleration is inversely proportional to mass, th...

posted 2y ago by celtschk‭  ·  edited 2y ago by celtschk‭

Answer
71%
+3 −0
Q&A How can the kinetic energy equation be intuitively understood?

Change in momentum is force times time. On the other hand, change in kinetic energy is force times distance (more accurately, the component of the force along the movement times distance; a force p...

posted 2y ago by celtschk‭

Answer
66%
+2 −0
Q&A How to find position of a particle at a time given a position dependent force

In general, the only way to do it is to solve the equation of motion. In simple cases, that can be done analytically (that is, you can find an explicit formula, but in most cases (outside problems ...

posted 2y ago by celtschk‭  ·  edited 2y ago by celtschk‭

Answer
66%
+2 −0
Q&A Prove differential form of Lagrangian

Let's first remember how you check that you are at an extremum (minimum, maximum, saddle point) of a normal differentiable function. You do so by checking that the first derivative is zero (plus fu...

posted 2y ago by celtschk‭  ·  edited 2y ago by celtschk‭

Answer
66%
+2 −0
Problems Find equation of motion using. Lagrangian given equation is $L'=\frac{m}{2}(a\dot{x}^2+2b\dot{x}{y}+c\dot{y}^2)-\frac{k}{2}(ax^2+2bxy+cy^2)$

Your mistake is that you did a second derivative of $L$, taking the derivative according to both degrees of freedom together. Instead you need to make a separate equation for each degree of freedom...

posted 2y ago by celtschk‭

Answer
60%
+1 −0
Q&A Clear up confusion on Minkowski signature

As you probably know, one of the postulates Einstein's Special Relativity is based on is that all observers see light in vacuum go at the same speed $c$. Now consider a lamp at rest relative to Jo...

posted 2y ago by celtschk‭

Answer
50%
+0 −0
Q&A maxwell equation in 1d

Yes, that would the obvious interpretation of that equation in one dimension. Note also that in that case, the divergence also reduces to the ordinary derivative. In other words, in one dimension,...

posted 1y ago by celtschk‭

Answer