# Questions tagged [length]

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### Is length contraction just a rotation in spacetime? [duplicate]

I am trying to understand length contraction in special relativity, in an intuitive way. So I am trying to visualize this phenomenon in the following way, and I would like to know if my example has ...
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### Post flagged as duplicate but I still don't know the answer to my question! [migrated]

This post was flagged as duplicate to this but I couldn't understand all the replies very well. Mr John Rennie's reply seems to agree with my initial thought process, but I could be wrong; Is the ...
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### Help me understand length contraction in an intuitive way—length contraction as four-dimensional rotations? [duplicate]

I am trying to understand length contraction in special relativity, in an intuitive way. So I am trying to visualize this phenomenon in the following way, and I would like to know if my example has ...
• 35
46 views

### What is the proportional relation between effective length $L$ and gravitational acceleration $g$ for a simple pendulum?

The formula of time period of a simple pendulum stands for, T =2π √(L/g). ● If 2π and g remain constant, T would be proportional to the square root of L. Saying, T ∝ √L and T1/T2 would equal √(L1/L2). ...
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### How to define approximate meter using primitive to no tools? [closed]

Imagine you've lost somewhere in the wild due to some catastrophic event, and don't have any measurement tools with you. How do you find approximate meter, millimeter, etc. with materials like sticks ...
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### Relation Between Power, Distance, Time and Mass

I was calculating something and reached this equation $${Meter^2 \over Second^3} = {Volt * Ampere \over Kg}$$ Is it correct? Cause if it is... It will tell me I am on the right path.
1 vote
1k views

### Length contraction speed of light

The Special Theory of Relativity tells us that a moving object eg spaceship measures shorter in its direction of motion as its velocity increases. At the speed of light it would have zero length, but ...
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### What is superconducting coherence length?

I'm an electronics student, and don't know much about some physics concepts. I was studying superconductivity and came to the London equation, Meissner effect and BCS theory. I kind of understood ...
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### If I cut a string, will its length be rational or irrational? [duplicate]

If I cut a string (lets say approximately halfway), will the length of each side (in inches) be rational or irrational?
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### How to construct a 12-micron thin layer of powder+epoxy?

Okay, this is more of an engineering tactic question perhaps, but any insight into any possible process will be very, very appreciated. So I'm mixing a powder with epoxy, making a pasty, fluid semi-...
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### Imperial to Metric lenght [closed]

I'm from Metric based country and have an unusual for me imperial notation. Google didn't clear that up for me so I'm asking it here: I have a wall with measures: 10'7-1/4'' What's 7 ? is it tenth of ...
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### What is the spacetime unit?

So we have a graph of space vs. time, space being $y$, time being $x$. What's the unit for the distance between them? $$\sqrt{(y m)^2+(x s)^2}$$ $$\sqrt{(3m)^2+(4s)^2}$$ \sqrt{\frac{(3m)^2}{(3 m)^...
1 vote
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### Holograms - interference image, can I tell if the 2nd diode is good for holograms by comparing fringes?

I've created two fringe images - one of a laser diode that's able to make holograms which outputs 5mW. The second laser outputs 20mW and so far I've not been able to make a hologram with it. I had a ...
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### relativity length contraction for twin clock experiment

The question im going to ask is based on scenario given here https://www.scientificamerican.com/article/how-does-relativity-theor/ Only thing that's different is that spacecraft has a length of 1 ...
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### Bandwidth-length product of an optical fiber

A multimode step index fiber has a numerical aperture of 0.2 and a core refractive index of 1.47 . Estimate the bandwidth-length product for the fiber assuming only intermodal dispersion when: (a): ...
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### A question about the definition of proper length

As I understand it, the proper length of an object is defined as the length of the object in its rest frame. In terms of the metric it is defined as the length of the spacetime interval between two ...
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### How to read this length interval in imperial units?

I am from Europe and I do some research for my thesis. I found this picture, which is very usefull for me, but unfortunately the lengths are in imperial units (for lenght they are using something like ...
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### How to calculate the diameter of a moving circle from afar while lacking and knowing some information?

Let's say there is a solid wood wheel with two tires attached at the bottom travelling on a level road towards me while facing me width-wise (as in, the side of it from which you can see its diameter)....
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### Does limiting to infinity violate laws of physics?

It is noteworthy that one cannot simply divide any length more than the Planck-length. If so, one cannot simply divide any volume more than the $(Planck-length)^3$. So if I want to find the limit of ...
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### Why isn't a meter defined from a kilogram of water?

Why are there different official definitions for a kilogram and for a meter when a meter can be defined by the volume of a kilogram of water? For instance, using the triple point or some other state ...
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### Can you express mass in other dimensional units?

I'm just started a Physics I course, and while I've paid attention, I'm stuck on one of the first problems: Express mass ($M$) in terms of acceleration($a$), density($D$), area($A$), and time($t$). ...
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### Proof for Resistance is directly proportional to length and inversely proportional to the area of cross-section?

I have heard that Resistance is directly proportional to length and inversely proportional to area of cross-section. Can someone give me a practical explanation for this?
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### Where is the logical hole in this reasoning? (special relativity)

I cannot see the problem in the following reasoning, so I'd be glad if you could help me out. The problem is defining a notion of "length" that is consistent with the constancy of the speed of light ...
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1 vote
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### Does the ratio of magnetic length to geometric length of a bar magnet always remain the same?

It is said that, due to end effects, the assumed poles of a bar magnet are slightly inside the ends of the magnet. The distance between the locations of the assumed poles is called the magnetic length ...
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### Proper length in GR

What meaning/use is associated with the notion of proper length in general relativity? Do you know an example of any quantity that depends on it? I have so far found statements like "the length ...
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### What Is the Physics principle behind dropping a stone into a cup of water?

I have been doing an experiment about relationship between drop height of a stone and the loss of water in the cup it lands in. I found that after dropping the same stone into a cup with the same mass/...
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