All Questions
42 questions
-1
votes
1
answer
110
views
Speed is equal to distance divided by time but is this correct?
In this study https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9784821/, the distance the punch travelled from start to impact is 0.49 meters and the time taken from start of punch (that's it, they define ...
- 364
1
vote
1
answer
35
views
Question about light and distance
If we see into the past with light and distance travelling so we can’t see things how they are currently, only how they were in the past; and James Webb took a photo from the beginning of the universe ...
- 11
1
vote
0
answers
45
views
How can we accurately tell distances of celestial bodies when considering superluminal expansion [closed]
If parts of the universe are moving away from each other faster than the speed of light relative to my position in space, how can we accurately tell the age or distance of other celestial bodies ...
-1
votes
2
answers
87
views
Explain the equation
Can someone explain me this equation. This is braking distance equation that applies all reaction times ect.. Taken from Bosch Automotive Handbook.
But what does the 25,92 mean there?
v= velocity
tvz =...
- 43
-1
votes
1
answer
86
views
Estimating penetration depth of projectile in nonhomogeneous material
I need an equation for calculating the penetration depth of a projectile in a non-homogenous material. I have the values for density of each layer and the projectile, speed, and angle. Does anyone ...
2
votes
0
answers
71
views
Number of meetings of $2$ cars starting from opposite ends of a road [closed]
Question:
$2$ cars travelling at $108,75$ kmph respectively, start from the opposite ends of a $90$ km straight road. Travelling back and forth continuously for $10$ hours, how many times do the $2$ ...
- 177
-1
votes
1
answer
69
views
Derivative of distance [duplicate]
I know that $speed = |\frac{\vec{dr}}{dt}|$
and first derivative of distance with respect time will be $\frac{d\vec{|r|}}{dt}|$
These 2 expressions don't seem to represent the same thing. But when I ...
0
votes
2
answers
140
views
Does equations of motion work for distance and speed? [closed]
In some books,when solving to find the distance and speed of the object having motion in straight line,the three equation of motion are used.so my question is whether these equation of motion (i.e $v=...
- 31
1
vote
1
answer
333
views
Distance given two velocities
I have a home trainer that is connected to an application that I am writing which needs to calculate a distance traveled given the speeds that the trainer is sending.
As such, every second, the ...
- 13
0
votes
1
answer
217
views
How to calculate the speeds two objects need to move at in order to reach different destinations at the same time [closed]
For example: On a graph there are two points. Each point has a different destination. The distance between Point A and its destination is 50, and the distance between Point B is 100. The points will ...
- 11
0
votes
2
answers
187
views
Variables in rectilinear motion
I wrote a post few days earlier on circular motion but it seems i still haven't got the hang of it yet. When is this equation actually true?
$s=ut+\frac{1}{2}at^2$
Suppose velocity is given by $v=t-2$ ...
- 1,197
0
votes
2
answers
146
views
Is it possible to derive a distance time graph from a displacement time graph?
If I take the derivative of a displacement-time function, it will give the function of its velocity over time. If I take the absolute value of my velocity function it will give me a function of its ...
- 1
-2
votes
1
answer
102
views
The distance between two moving objects at the speed of light [closed]
Two objects move in the same direction at the speed of light.
If we look at one of these two objects, what does the distance between the two particles change? Does it stay the same?
0
votes
1
answer
50
views
How to use this equation in real life for accurate results?
In this video, you can use the equation to solve for the distance between the ball being dropped and when it hits the ground. All you need to know is the time it takes and the gravitational ...
- 415
1
vote
2
answers
162
views
Does adding weight to a person affect the time taken for a person to run 20 metres?
I am doing a science experiment to see if adding weight to a person affects the time taken for a person to run 20 metres. I am needing to write some background information (1 page) and I am not too ...
1
vote
3
answers
16k
views
How can I calculate deceleration due to friction?
I was wondering, how can I calculate the decelerations of an object due to friction - and therefore find the maximal distance it can reach?
For example, if a car suddenly brakes in the middle of a ...
- 41
3
votes
1
answer
126
views
Given a fixed average speed in the speed vs. distance graph, is it the fastest to travel constantly at that speed?
Is it true that among all the ways to travel a distance $X$ with an average speed $E$ in the speed vs. distance graph, traveling with a constant speed $E$ minimizes the time it takes to complete the ...
- 33
2
votes
1
answer
2k
views
What is the formula for how far a sound can be heard (taking into account dissipation)?
I was trying to figure out how far can a sound of 103 dB can be heard, so I converted it in W/m$^2$ (it gave me about $0.0200$ W/m$^2$) and then I used the formula “$I=P/4\pi r^2$” to find the maximum ...
- 41
0
votes
3
answers
294
views
What does the first derivative of (2-norm) distance with respect to time tell us?
My basic physics' knowledge is a little rusty. My apologies in advance. I know that the first derivative of position or displacement with respect to time is the instantaneous velocity. Suppose I have ...
0
votes
1
answer
547
views
Distance in seconds between moving vehicles
If two cars are moving in the same direction.
let’s say ego car is in the front and another follower car. the speed, location in x, y coordinates of both cars are given.
How to calculates the ...
4
votes
3
answers
154
views
What is the best way to conceptualise a 'division' [closed]
This may seem like a strange question, but my question is more along the lines of trying to figure out how people were able to 'discover' the formulas which have shaped our understanding of the ...
- 143
0
votes
1
answer
52
views
Different time for same amount of kph/mph change at different speeds
First of all excuse me if my english isn't perfect, and if the question is hard to understand, even I am a little confused about what do I even want to ask.
So I bought a new wristwatch not too long ...
-1
votes
1
answer
93
views
Definition of speed [duplicate]
Is speed the magnitude of the velocity vector or the travel distance divided by the travel time?
A common example shows the problem: circular motion. "When something moves in a circular path (at a ...
- 37
0
votes
1
answer
2k
views
Show that the initial speed of the block and the bullet, after they began to move off together, was 1.3 m/s
A bullet of mass 2.0g is fired horizontally into a block of wood of mass 600g. The block is suspended from strings so that it is free to move in a vertical plane. The bullet buries itself in the block....
- 177
-4
votes
2
answers
5k
views
Does differentiating a distance with respect to time give velocity?
I'm just wondering if you have a distance function:
$$
s(t) = 0.1t^2 - 5t
$$
where $s(t)$ is distance and $t$ is time in seconds, does differentiating it give you a function for velocity?
- 163
-3
votes
2
answers
102
views
Speed in min/km given distance in meters and time in seconds
How to calculate speed in min/km given distance in meters and time seconds? I used formula v = d/tbut having problems converting units.
I've tried ...
2
votes
1
answer
7k
views
How many times does plasma do a full loop tokamak before fusion?
From this photo I assume the plasma is also moving in a loop through the reactor due to it being a charged particle.
I have been trying to find a speed at which it does this but couldn't and neither ...
- 103
1
vote
1
answer
188
views
Why is speed not dependent on distance? (conservation of energy concepts involved)
as I'm beginning to learn the basics of physics, there are some concepts that confuse me.
If I'm finding the minimum speed needed for a ball to roll up a hill, the equation is:
(1/2)mv^2=mgh
...
- 111
0
votes
3
answers
2k
views
Calculate the distance traveled when "braking" for fixed amount of time to a fixed velocity [closed]
I have the problem that I need to know how many steps I traveled when I go from velocity $a$ to $b$ in a fixed amount of time. I always know how long it will take me to go from velocity $a$ to ...
- 111
0
votes
1
answer
45
views
Gaining speed for further space travel [closed]
With the recent discovery of the new solar system with viable planets for sustainable life, a thought of prior discussions intrigued me. Now, please understand that I have no engineering background, ...
- 1
0
votes
2
answers
387
views
Given a known total stopping distance, how can I calculate the initial speed?
This would be my first question on Physics.stackexchange. As I looked closely if I would not double my question, I try dare to ask the question.
I am doing some calculations together with my kids. ...
- 103
-1
votes
1
answer
642
views
Modeling a waterfall
I'm modeling a waterfall, the water streams out of a rectangular box with a width of $\text{W}$, a length of $\text{L}$ and a hight of $\text{H}$, so the volume of the water that is streaming from a ...
- 291
0
votes
1
answer
96
views
Is there any proof about mathematical definition of constant speed agreeing with intuition?
First, I wanna clarify that I understand the intuition behind the definition of velocity in 1, 2 and 3-D (The derivative of the position vector).
But the other day I was thinking if that definition ...
- 45
0
votes
1
answer
86
views
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)....
- 35
-1
votes
1
answer
141
views
Can motion be characterized without time as independent variable? [closed]
I was just thinking about speed = distance/time which relatively describes how fast something is moving wrt some still object.
So if by some wishful thinking or some coordinate system I remove the ...
0
votes
3
answers
1k
views
How to tell if area is displacement or distance?
why is it not called "velocity v. time"? how do you know?
If the y-value can be either positive or negative, the direction is then indicated. i think this is why it should be called velocity but not ...
- 1,381
0
votes
2
answers
61
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 ...
1
vote
1
answer
2k
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 ...
0
votes
1
answer
951
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 ...
- 103
-1
votes
1
answer
2k
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 ...
3
votes
2
answers
331
views
How much more energy would I spend if my bicycle was 2 kilos heavier? [closed]
I have a bicycle weighing 8 kilos. An 10 kilometer ride averaging 20 km/h requires z kWh's of energy.
How much more energy would I spend if I added 2 kilos to my ...
- 139
0
votes
1
answer
836
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 ...
- 223