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-5
votes
3answers
33 views

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

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 ...
4
votes
3answers
603 views

Work = Force x Distance vs Displacement

The difference in using Distance vs Displacement is demonstrated in this example: Work = Force x Distance If I carry an object to and fro 10 metres, the work done would be Force x 20 metres. ...
1
vote
0answers
23 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 ...
0
votes
2answers
38 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, ...
2
votes
1answer
42 views

How can I set up an equation for distance traveled for a rubber band powered car?

I am to make a rubber band powered car, and I have to maximize it's distance traveled. The time taken to reach said distance, top speed of the car, acceleration of the car, is not relevant. I just ...
0
votes
1answer
29 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
0answers
23 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
54 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 ...
1
vote
2answers
66 views

Force when distance between charge is zero

According to coulomb law $$ F = \frac{q_1q_2}{r^2} $$ I want to know what happens to force when $r=0$. If $F \to \infty$ then the charges can't be separated! But if an unlike charge of higher ...
0
votes
3answers
64 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 ...
3
votes
1answer
90 views

Do we actually measure distances in light years?

The cosmic distance ladder has a wide range of length scales, which are quite difficult to measure and to conceptualize. These distances are commonly quoted, particularly in less technical articles, ...
1
vote
0answers
32 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 ...
-2
votes
1answer
28 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 ...
2
votes
1answer
38 views

Does the line integral definition of Work involve distance or displacement?

My textbook reports the following definition of Work: where ds is the infinitesimal displacement. I know that an infinitesimal displacement is usually denoted by dr and I also know that the ...
0
votes
1answer
80 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 ...
2
votes
1answer
223 views

Difference between Gunn Peterson trough and the Lyman Alpha Forest? Cosmological implications?

I'm having difficulty understanding the full implications of the Lyman alpha forest and its use in cosmology. My understanding is this: we detect features in the Intergalactic Medium (IGM) by very ...
0
votes
4answers
63 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
1answer
40 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
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
29 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 ...
1
vote
0answers
77 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
2answers
84 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 ...
4
votes
2answers
201 views

How were the ratios of distances between planets and the Sun first calculated?

I was reading some literature and I found that long before the actual distances between other planets and Earth or distance between Sun and Earth were known, physicists had calculated the ratios ...
0
votes
1answer
35 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
143 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 ...
2
votes
1answer
70 views

How the distance and diameter of the stars are experimentally measured?

How to measure the distance of a star and the diameter of it from earth based tools? Normally we can measure the angle between the stars edge. But diameter or distance needed to measure the other ...
-1
votes
2answers
101 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 ...
0
votes
1answer
83 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 ...
2
votes
3answers
346 views

Will an un-scattered photon go to the edge of the universe? [duplicate]

Will an unhindered (un-scattered) photon go to the edge of the universe?
0
votes
1answer
31 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
51 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), ...
2
votes
1answer
78 views

Measuring more accurately the distance of remote galaxies

From what I read in Wikipedia, the velocity of a Galaxy has two components: one is due to Hubble's law for cosmic expansion, and the other is the peculiar velocity of the galaxy. Since the peculiar ...
1
vote
2answers
48 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?
0
votes
1answer
219 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 ...
1
vote
2answers
87 views

Speed of light and distance

Our measure of distance (the meter) is defined in terms of how far light in a vacuum travels in a specific time. When light travels through another medium, we say it travels at a different speed. Why ...
0
votes
1answer
109 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, ...
2
votes
1answer
61 views

Distance from redshift

I am looking for a exact derivation of a relation between redshift $z$ and distance $d$. What I know is the definition ...
3
votes
2answers
65 views

How are the distances to the most distant $\gamma$-ray bursts measured?

This question came to my mind when I read on NASA's website that an explosion (gamma ray burst, GRB 080913) took place 12.8 billion light years away from us. How do they measure such large distances?
1
vote
3answers
494 views

Calculate vertical distance using acceleration

I have the following scenario: an iPhone is connected to a vertical rail (it's motion is restricted to the Y axis). Through mechanical means the phone is forced upwards and then allowed to return to ...
7
votes
1answer
1k views

The physics behind Google Glass' “prism”

In writing a bachelor's thesis about applicable use cases for Google Glass in retail I also strive to explain the physics behind Glass' optics. So far I've come to the following conclusions: Glass ...
0
votes
0answers
30 views

Angular diameter distance in an inhomogeneous universe?

Computing the angular diameter distance $D_{A}$ is a well known academic exercise in an homogeneous Universe. But now suppose that we are in an inhomogeneous Universe and that I am interested in ...
2
votes
1answer
73 views

random particles on a grid: Effect of increasing density on distance between them

Say I have two boxes which both contain, say, 25 red particles (as shown in picture). These particles are randomly placed in a 2d grid, and in one the total area $A_{1}=20000$ and the other has area ...
0
votes
2answers
190 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 ...
15
votes
2answers
2k views

Why does one get an illusion as moon following him?

When you run or ride bike at night if you observe the moon you feel like he moves along with you as the same speed you are going. Why?
2
votes
3answers
96 views

How to calculate the velocity of this body? [closed]

Graph of a train (the body) is provided which starts from rest. What is the velocity after the train has 10 metres displacement? Thats the only things provided for the question, please help me ...
1
vote
1answer
52 views

Luminosity distance from angular diameter distance

Consider that I know the cosmological angular diameter distance at a given redshift : $$D_{A}\left(z\right)=\frac{x_{object}}{\theta_{observer}}$$ Is there a general formula to compute the ...
2
votes
2answers
141 views

How is time distributed through space?

I was greatly confused when I saw video saying that if two wormholes were separated by time instead of distance, it would allow time travel. My question is what did they mean by this statement? What ...
0
votes
1answer
42 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
267 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 ...
3
votes
0answers
75 views

What is the maximum range of a bullet flying through the sky? [closed]

How far would my bullet fly with the following characteristics? 1.2km/second initial velocity 45 degree angle into the sky 'Normal' atmospheric conditions No wind Typical high-powered rifles have ...