# Tagged Questions

The tag has no usage guidance.

735 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 ...
168 views

### Is there a finite unit of distance that we cannot divide past?

If distance could be divided into an infinite no of units or points, then it seems to me that motion would be impossible since a meter for instance, having an infinite no of points within it (and the ...
3k views

### Calculate the distance between two points from iPhone Camera

I want to calculate the distance between two objects using an iPhone camera. Suppose I'm standing with my iPhone 10 feet away from the objects. Now, I want to calculate the distance between those ...
871 views

### What is the apparent diameter of the sun as seen from earth?

I know this may not be physically accurate. For my purposes, basically 3D renders, I am assuming the sun rays are parallel rays from an infinitely far lamp. If the sky is clear, what size would that ...
99 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 ...
98 views

### How Far Does Gravity Extend? [duplicate]

How far does gravity's influence extend? I've recently (re-)seen 'The Universe' season 1 where it's said that 'take these two dice, place them perfectly still in empty space 1 inch apart and within ...
121 views

### How far do we need to be removed from the earth to show the curvature with a viewing angle between 42 and 48 degrees? [duplicate]

I have seen already a couple of answers but none of them give an exact number of what should be the minimum height where we would be able to record the curvature of the earth All I could find is ...
255 views

### Is it possible to calculate the dimensions of ANY object in a picture having at some known distance an object on know dimensions?

Is it possible to calculate the dimensions of ANY object in a picture having at some known distance an object on know dimensions? I'm thinking about the scenario where someone is holding a smartphone ...
186 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 ...
20 views

### size at a distance

Can someone help me please. If I held up my thumb at full arms length into the sky. My thumb is the width of an object I am looking at, at 2000 meters away. How big is the object in the sky?
54 views

### Is there an underlying reason why some forces are inversely proportional to the square of the distance? [duplicate]

This is the first time I'm studying those subjects (I'm still in high school) and my teacher couldn't give me an answer. I'm referring specially to Newton's law of gravitation and Coulomb's law of ...
88 views

### Distance can be zero

Can a distance between two particles can be exactly zero? Example: If I have two opposite charged particles having uniform charge. They will attract each other and the distance between them will ...
39 views

### When measuring distance how do we know when supernova comes from binary star and not single one?

The way I understand distance is measured for far out objects is by binary star supernova, since at the point of explosion there's is always same amount of energy released. But then supernova can ...
65 views

### Can meters measure a distance in higher dimensions?

Consider meters as a unit of measurement. Meters can, of course, be used to express distance across a two-dimensional plane. E.g. The distance from your chair to the door is 2 meters. Meters can also ...
68 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 ...
57 views

### Projectile motion with air friction force/resistance [closed]

We have to find the x (the distance, if you didn't know that then I'm not sure if you should be doing this problem) that the projectile travel during the time in the air until the time it hits the ...
57 views

### How does one calculate how big something has to be, to be seen at a given distance? [closed]

Ignoring curvature of the Earth. How do I calculate the size an object would need to be in order to appear to be approx 1cm tall at a given distance?
27 views

### Distance formula using initial velocity and acceleration

we know $S=ut+1/2at^2$. Now lets say my initial velocity $u=10m/s$ and acceleration be $a=5m/s^2$. In first second distance traveled $S^{_t=1}=10m$ as my speed is $10m/s$ and time is $1s$. In next ...
106 views

### Distance from Earth where gravity becomes negligible

This is a basic little problem I thought up when trying to remember some physics, and I wanted to see if it's at all correct: trying to figure out the distance from earth where gravity becomes ...
60 views

### Difference between Distance and Space

So I take particle A and place it in space, then I place particle B 1,000,000 light years away from particle A. I strike a line between the two, and measure that line as having a length of 1,000,000 ...
330 views

### Is displacement in circular motion a chord or an arc?

When taking the displacement between two points along a circular path to calculate its velocity, do you take the length of a chord connecting the two points or do you take the length of the arc ...
97 views

### Would a giant see our year as a second? [closed]

If there were an enormous being whose arm span is one light year across, how would that being perceive time? Wouldn't what we perceive as a year be virtually nothing to that being? Explanation: "...
414 views

### How to calculate distance travelled while car is rolling, given start and end speed?

I'm trying to calculate the distance travelled by my Formula Student racecar if it starts at a certain speed, goes into Neutral (no acceleration, no brakes, just rolling on its wheels), and ends at ...
329 views

### How can we see objects that are so far away? [duplicate]

The HUDF used to be the deepest image of the universe ever taken by the Hubble telescope, the furthest star in this image is 59000 light years away. The star in question: Now Imagine a light ...
206 views

### How do I graph acceleration?

I have written some java code for the calculation of some various acceleration and etc. type data. I am now trying to graph that data so I can pull specific data over a time line. The values I have ...
123 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 ...
55 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?
1k 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 ...
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 ...
58 views

### What type of instrument can I use to determine my current distance from the center point of Earth?

Immediately, I think of a scale, but is there better way? I can only imagine weighing an object of known mass with an extremely precise scale. I am asking because I would like to be able to address ...
24 views

82 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 ...
185 views

### If there is a boson that carries mass, why not space, or time? [closed]

If the Higgs Boson carries mass, why doesn't there exist more bosons that carry other fundamental properties such as volume/distance (space), time, or even spacetime? Also if bosons carry force, but ...
47 views

### Packets of information in the real world

Please excuse this apparently naive question. no one appears to have the answer. If a standard packet of data is travelling down a standard fibre, what is the physical time taken between the first ...