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1
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4answers
45 views

Are wavelength and the distance same thing?

Can you clarify for me the following question: are wavelength and distance same? I know wavelength is measured in terms of distance but when we have a look at the two equations: $$ c=f\,\lambda\\ ...
1
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2answers
50 views

Time, distance perception [duplicate]

If photons going c have no local time or distance 'perception' why isn't the same true for us as we're going c relative to them?
1
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2answers
811 views

1D Kinematics - Relative Motion involving non-inertial frames of reference

I recently came across a question involving non-inertial frames of reference. I didn't quite understand the way it had been solved due to some conceptual confusion regarding certain deductions made to ...
1
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1answer
1k views

Relation between comoving distance and conformal time?

In cosmology, we have two quantities and I want to understand the physical relation between these two : $\chi = \int_{t_e}^{t_0}c\frac{dt'}{a(t')}$ : the comoving distance with $t_e$ the time at ...
1
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0answers
25 views

Help with finding an equation to work out the length of cable required to produce loss of colour on an analogue video signal

When I briefly taught Broadcast Engineering I set up an experiment in order to demonstrate the effect of signal reflections along coaxial cable on an analogue PAL waveform. It involved getting the ...
1
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0answers
37 views

What technologies are available to measure distance? [closed]

I'm a programmer, I really lack of physics knowledge, I'm trying to make some basic design for a distance measuring simple system, for a social project I'd take as hobby. Basically I would have many ...
1
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0answers
80 views

Which physical entities equal “distance times time”?

Are there useful physical quantities with dimensions of distance-time? The background for this question is a differential equation which I try to make sense of: ...
0
votes
3answers
72 views

Why is there a contradiction in this Newton's equations of motion related question? [closed]

One second after being thrown straight down, an object is falling with a speed of 20 m/s. How much distance does the object travel in the first second? We took: $$v = 20\,{\rm m/s}$$ $$u = 0\,{\rm ...
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votes
4answers
65 views

Using formula for work with distance of 0m [duplicate]

Consider this: Wind is pushing a huge rock towards me at with massive force at 2m/s. I push against the rock at equal force so the rock stays still. I am clearly "working" very hard, using a lot of ...
0
votes
2answers
94 views

Solving distance with acceleration and velocity given and getting two different answers using two different equations [closed]

Frictional forces from brake pads are responsible for stopping an automobile. A car is moving at $35.0 \:\mathrm{m/s}$. If the car's brakes are capable of generating a deceleration rate of $6.00 ...
0
votes
1answer
96 views

How to measure distances to stars by means of spectroscopic parallaxes?

How to measure distances to stars by means of spectroscopic parallaxes on practice? What is the accuracy of measuring distances using this method compared with distances based on HIPPARCOS ...
0
votes
2answers
142 views

Distance travelled in spaceship Newton vs Einstein

If you get in the canonical 1G windowless spaceship and accelerate for 5 years as determined by your trusty wristwatch, then decelerate for 5 years, then decide its time to see where you are would the ...
0
votes
1answer
40 views

Distance to the galaxy which has velocity which is perpendicular to the point of view of the static observer

Let's have the galaxy which has velocity which is perpendicular to the point of view of the static observer in the FLRW universe. It emits the light. There is a given redshift $z_{0}$. It will be easy ...
0
votes
1answer
108 views

How do we know that time and distance are not discrete?

I know that it is believed that energy is discrete, in that it travels in quanta. I was wondering if there is any evidence which either proves or disproves something similar with both time and ...
0
votes
2answers
49 views

A car is moving in a circular trajectory with radius R=20m. The equation of motion is : x(t) = 15 + 8t – t^2 [closed]

We have to find the distance the car has traveled after 3s. Actually this question came up in an important exam, and the answer was: L=x(3)-x(0) But I think this is the answer for displacement, ...
0
votes
1answer
43 views

Why is parallel component of velocity along position vector considered rate of change of position?

If you have a position vector and a velocity vector of a particle, then the component of velocity vector along position vector is the rate of change of distance of the particle from the reference ...
0
votes
1answer
41 views

Given any metric, how to find the straight line path between two points? [closed]

Say we are given a two-dimensional metric $$ds^2=f_1(x)dx^2+f_2(x)dy^2,$$ for any kind of function. How do we calculate the distance along a straight line path (not the shortest possibly) between, ...
0
votes
1answer
44 views

Calculating distance between two objects viewed from an angle [closed]

I'm trying to determine the location of this vehicles rear bumper and the front edge of the white road marker. I can't tell if the vehicle is before, at the edge, or just ahead of the marker. The ...
0
votes
1answer
89 views

Distance as a function of time where acceleration changes with respect to distance

I was thinking the other day about gravity. I know that acceleration in a magnetic field changes with respect to distance from the center of the field. So I was thinking, how would one find the total ...
0
votes
2answers
56 views

Is in this case distance same as displacement? [closed]

I have this graph, and I need to know the displacement in the interval from 0 to 5 seconds, so I found the area of the rectangle that you can see there. A = w*h, which means X = (5 seconds)*(20 m/s), ...
0
votes
1answer
253 views

What distance does one travels in his lifetime? [closed]

I think this isn't answerable without having point of reference from which speed at which earth travels in space, however if I am wrong the please give absolute distance. Considering that earth spins ...
0
votes
1answer
145 views

Why do we observe opposite motion of trees (nearer) and trees (distant) when seen from a moving frame? [duplicate]

If you are in a moving train or in a bus, what you observe is that the trees which are nearer to you move opposite to the direction of your motion. But the trees which are very far away from you, ...
0
votes
1answer
44 views

Compute the minimal distance between two points in movement

There are two points, $A$ and $B$ that move according to these laws: $$ \vec{x_a}= 20 -10 t $$ $$ \vec{x_b}= -15 +15 t $$ $A$ moves along the x axis, $B$ along the y axis. I have to compute the ...
0
votes
1answer
290 views

Distance travelled given velocity at various moments of time [closed]

I am trying to solve a problem where I need to find the distance travelled at the end of the nth second and my input data contains only velocities at different time instances. Say for instance I ...
0
votes
1answer
126 views

find distance using a light line

Let's suppose we have a particular light frequency emitter and relative sensor array, and that there is no external source of this light. This emitter has a know angle respect the receiver, and emit ...
0
votes
1answer
11k views

Finding deceleration and velocity using distance and time

A car is moving down a street with no brakes or gas. The car is slowing due to wind resistance and the effect of friction. The road is flat and straight. The only data I have are timings taken at 100m ...
0
votes
1answer
28 views

How is the diameter of a nucleus measured? [duplicate]

From what i know, some statistical analysis is utilized in doing so. First, you take a thin slab of material, then fire particles which will reflect off the nuclei of the atoms in the material. The ...
0
votes
0answers
32 views

Luminosity distance as a function of redshift

We know that the luminosity distance is: $d_L = a_0 R (1+z)$ with $z$ the redshift. How can we mathematically make explicit the dependence of $d_L$ from the redshift? I guess we need to make it ...
0
votes
0answers
57 views

measuring distances

We measure distances using half of the time of flight of light, 'a la Einstein'. What is the geometrical shape of the surface that is the locus of the points that are at a definite distance of an ...
0
votes
1answer
104 views

Car Motion: Power and Distance: Air Drag [closed]

I need to workout the amount of Power required by a car, in order to overcome air drag forces. I have figured out that, Power = c(Velocity^3). But, I am unable to understand Power's relation with ...
0
votes
0answers
28 views

The path that light travels [duplicate]

This is a question that has puzzled me for some time. As a star emits light, the light travels away from the star. If you were to pick any spot on the star and draw a line extending outwards and then ...
0
votes
1answer
41 views

How to use radio waves to calculate distance over short distances?

I read an article about a company that created the equivalent of a GPS location system for internal spaces where the satellite based GPS is blocked. They made reference to the Fresnel number as to ...
0
votes
1answer
167 views

Finding acceleration and distance when velocity given

I am trying to do the following question for practice (it is an interview question), and I don't know if my methods and answer are correct. Given a velocity $v=2+3t^2$, find acceleration after 3 ...
0
votes
1answer
33 views

Finding the distance between two osclilating particles in a wave

Assume a wave function $\psi = \psi(x,t)$ where $x$ is position from the starting point $(0,0)$ and $t$ is time. Two oscillating points A and B are located at $x_1$ and $x_2$ respectively with $x_2 ...
0
votes
2answers
236 views

Observer looking out through the window of a train [duplicate]

When travelling by a train, it seems that the nearby objects move in the opposite direction(which I can explain) but the distant objects appear stationary. I can't explain this. By the concept of ...
0
votes
1answer
528 views

Simple Acceleration Problem throwing me off

I am having trouble with this problem from my homework. I have gone over it many times, and I must have some concept wrong. A rocket is launched from the ground with constant acceleration. After 4 ...
0
votes
1answer
91 views

Is there any case where one would use, snap, crackle or pop? [duplicate]

As we all know, if you differentiate distance with reference to time, you get speed, and likewise, differentiating speed you get acceleration. However, if you keep differentiating, to the rate of ...
-1
votes
1answer
6k views

How light years is measured? [closed]

How are light years are measured? I remember the distance between earth and moon are measured by the delay in light which travels and comes back. But how are light years calculated?
-1
votes
1answer
297 views

Calculation of 12000 Lunar Orbits/Earth Day [closed]

I am really interested in the calculation of the following speed value in meter-per-second unit: Speed of something that is able to travel in one earth day the distance that it would take for the ...
-1
votes
1answer
37 views

Find Distance with Acceleration and Time

I'm working on Physics homework and have run into a problem I can't figure out. Any help would be much appreciated! Problem: Allison exerts a steady net force of 50N on a 22-kg shopping cart ...
-1
votes
2answers
134 views

What is the difference between the actual distance covered by a projected object and the displacement?

What is the difference between the actual distance covered by a projected object and the displacement? A stone was projected with an angle of projection of 30 and it covered a horizontal distance ...
-1
votes
1answer
154 views

Determine the distance from time-velocity graph [duplicate]

A small car that we made in class was travelling and its time was recorded at 1,2,3, and 4 meters. The points in the form (seconds, meters) are as follows: ...
-1
votes
1answer
361 views

Distance and displacement of an object on a straight line [closed]

I had this homework problem, but don't actually know if what I did is right, or that I even read the problem correctly. Can someone please tell me if this is the right interpretation of the problem ...
-5
votes
3answers
47 views

How to calculate meters per second speed when i have distance in meters and time in minutes [closed]

It might be a simple formula but I want to confirm it so can you please tell me how can I find speed in meters per second when I have Distance = 7720298 meters and total time 320941.03 minutes. How ...