In everyday use and in kinematics, the speed (commonly referred to as v) of an object is the magnitude of the rate of change of its position with time or the magnitude of the change of its position per unit of time; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero.
Speed has the dimensions of distance divided by time. The SI unit of speed is the metre per second (m/s), but the most common unit of speed in everyday usage is the kilometre per hour (km/h) or, in the US and the UK, miles per hour (mph). For air and marine travel the knot is commonly used.
The fastest possible speed at which energy or information can travel, according to special relativity, is the speed of light in a vacuum c = 299792458 metres per second (approximately 1079000000 km/h or 671000000 mph). Matter cannot quite reach the speed of light, as this would require an infinite amount of energy. In relativity physics, the concept of rapidity replaces the classical idea of speed.
I think when the speed of light was measured (and predicted from Maxwell's equations) that the assumption was made that this speed was a cosmic speed limit
Suppose that the cosmic speed limit was higher than c (not infinite) and that perhaps another form of radiation traveled at that speed...
Assuming that the observer moves along the direction of the light, does the speed of the observer's measuring instrument relative to the light source (which may be close to the speed of light) affect the brightness and/or power flux density measured by the observer?
I'm not sure about this...
This is the problem,
This is the textbook solution ; i think the textbook solution is not correct!
My thought,
##S_{max}## will be given by $$\frac {dy}{dS}=0$$
$$\frac {dy}{dS}=\frac {-1}{400}S+\frac {1}{5}=0$$
$$S=80$$
It is maximum economy because ##y{''}<0##, i.e by use of the second...
Summary:: How fast does a human sized object(or a human) need move so I won’t be able to see it at all if it passes right next to me?
Im trying to figure out something in regards to the Flash movies/Flash series but I’m super bad at calculations and math :(
Do you think that mach 2...
Wawawawawawa! This was a tough one...:biggrin:
Find the question below;
Find my approach below:
We have the following equations;
1. ##v=30-0.5t##
2. ##v=30-1.5t##
Now the car changes its acceleration at some point i.e from ##-\frac{1}{2}## ##m/s^2## to ##-\frac{3}{2}## ##m/s^2## ...
I...
There is lots of good information online about shock waves but I'm not finding what I want.
If dynamite has a detonation rate of 6800 m/s does the shock wave travel at 6800 m/s? Is sound we hear 1 mile away the shock wave or the sound?
What speed is an atom bomb shock wave?
This large horn...
This is a textbook problem (Mechanics).
Attached find the question and respective solution.
This is fine with me, i like trying different ways of solving math related problems. My approach is as shown below.
Using the graph sketch
It follows that,
##s##= ##(35×12)##+##\frac...
If two people are holding a stick going from the Earth to the moon and the one on Earth pulls the stick, would the person on the moon feel it immediately?
This question was answered on Quora and the answer given involves the speed of sound and claims that the person on the moon would not feel...
Why we know that average speed of a single photon(in point particle view) equal the speed of EM wave?If average speed of a single photon smaller than c then there exist massive photons?
Is the accuracy of 10^-12 s achievable in measuring a neutrino's speed with current experiments? I have come across a number of papers stating the accuracy is in the order of nanoseconds. This is much lower accuracy than the measured speed of photons. I believe it is due to the difficulties in...
Let ##m_s = 0.05, m_{s_1} = 0.02, m_r = 0.12, L = 0.8.## be the masses of the two spheres, mass of the rod, and length of the rod. Then the work done by gravity when the rod reaches the vertical position is ##(m_s(L/2) - m_{s_2}(L/2))g## and the kinetic energy equals ##\frac{1}2 (\frac{1}{12}...
[Moderator's note: Thread spun off from previous thread due to topic/forum change.]
Time dilation sounds really weird, can i assume it has a logical explanation?
Two clocks with photo detectors are 100 kilometers apart at A and B. On the center of AB axis two light pulses are sent to the clocks , synchronizing them. Then a light signal is sent from A to B. The two stationary observers record the time from event at A to event at B. Is there a one way...
Sorry for the bad english.
This might sound stupid but I am pretty new the physics and i can't seem to find what formula to use on this problem when only the mass, gravity and height of the fall is given.
and i can't find a similar problem in the book, could someone give me any pointers?
Thanks...
First off, I'm probably totally incorrect on all of this, so feel free to correct me.
Second, I'm only 15, so please just be gentle and helpful when I'm totally off.
Now for my idea:
Have a huge vacuum and put lasers on the inside with hundreds of different lasers at different angles equally...
Hello there, I believe here I need to find the capacitance of the junction between the P-doped gate and N-channel. Then I could find the RC time constant although I am not sure if there's something more I need to find the speed of the JFET?
What I'm unsure of is the depletion width h to use...
Hi. I cannot find the correct answer to the problem.
Attempt:
Net Fx = T - Fg - fk = 0
Fk = 0.16(mgcos30) = ma
a = 1.3579 m/s^2
v^2 = u^2 + 2as
v^2 = 0 + 2*1.36*4.3
v = 3.417 m/s
Answer: v = 3.9027 m/s
What did I do wrong here?
I was doing a exercise which considerst he time it takes for light travels a glass with thickness proper D and velocity v. The speed of light is c/n inside the glass.
Now, my approach was to go to the glass frame, take the relative speed between the glass and the light using the trivial formula...
I don't really understand the question. A proton collides obliquely with another proton means that the first proton moves at certain angle with respect to horizontal?
This is my sketch:
Is that correct? If yes, is it solvable since there are so many unknowns?
Thanks
I know it's not possible to travel at light speed so this is just theoretical. As I understand it at relativistic speeds the distance you need to cover to travel to a destination are length contracted. If you were traveling at light speed is the distance between you and any object ever zero?
“incidentally, to a good approximation we have another law, which says that
the change in distance of a moving point is the velocity times the time interval, Deltas=vdeltat This statement is true only iF the Velocity is not changing during that time interval, and this condition is true only in...
Hi everyone! :)
While i watched rc jet exhibitions on youtube, i find that the most fast of this RC reached +700 Km/h. When i browse more information about the tourbine, i realized that for a hypothetical supersonic RC the mechanical system of the tourbine must have a complete air compressor...
"We know only where she was at intervals of one minute from the table; we can get a rough idea that she was going 5000 ft/min during the 7th minute, but we do not know, at exactly the moment 7 minutes, whether she had been speeding up and the speed was 4900 ft/min at the beginning of the 6th...
There was a lot of kerfuffle a decade ago about neutrinos possibly exceeding the speed of light, A re-analysis of events debunked this back in 2012 I believe, but I don't know if the issue is conclusively settled. Has there been any re-confirmation of the speed of neutrinos in any paper later...
Consider the situation where an observer at rest on the ground measures the frequency of a siren which is moving away from the observer at speed ##v_{Ex}##. Let ##v_w## be the speed of the sound wave. Let ##\lambda_0##, ##f_0##, ##\lambda_D##, and ##f_D## be the wavelengths and frequencies...
We know the speed of light is a constant but speed is just the measure of distance over time. If blue light has a shorter wavelength than red but covers the same distance / time does this mean that blue light has actually made a longer journey than red light in order to arrive simultaneously?
I...
Some people thought light speed is actually instantaneous which can be demonstrated by doing an experiment involving a taut clothesline and two clothespins. On each ends of the taut clothesline, put one of the clothespins on both ends and touch one of the clothespin will make the other one at...
As an object approaches a black hole’s event horizon, it experiences increasing gravitational time dilation, causing it to appear to an outside observer to slow down, until, at the event horizon, it appears to stop. An object traveling in space that increases its velocity from one...
In Richard Feynman's book "The Strange Theory of Light and Matter", in chapter 2, he explains how to calculate the probability that light from some source will be reflected by a mirror and be detected at some location. He explains how you sum up all of the probability amplitudes (represented...
I have attempted a solution using conservation of momentum. Could people help check if this solution is correct (the result looks weird), as the problem doesn't have solution with it.
$$
\begin{aligned}
\begin{pmatrix}Mc \\ 0\end{pmatrix} &= \begin{pmatrix}E_R/c \\ \mathbf{p}_R\end{pmatrix} +...
The universal speed limit is c, and as a consequence light is confined to that limit. I was thinking about the time dilation in SR and was wondering if this is result of reaching speeds close to the speed of light or because of reaching speed close to c?
For example, let's say light could be...
The question is simple. The molten stuff inside the Earth will get a smaller volume when it solidifies. Will the Earth increase its rotation speed in reaction to this? What about the magnetic field?
I watched a Fermilab video on light propagation in water: . He says (~) at time 7:50:
"The oscillating electric field of the light make electrons in the glass move. These set up a second oscillating electric field that combines with the first to make a single oscillating field. That is the wave...
This is one of my thought experiments where I am drawing a big blank, If you have 2 objects approaching a 3rd object from opposite directions (just enough off to avoid collision) at 75% of the speed of light, the first assumption is that each observing the other would see the other object...
Hi, I'm working on a project to see if deliveries, pick ups, or both combined are better for the environment / more energy efficient / more time efficient. For example, (a) everyone collecting from a farm by bike, (b) vans bringing to supermarkets and then people collecting from supermarkets, or...
I am an Engineer, so I have some knowledge about physics and calculus. I've seen relativity in university years ago but only briefly. The majority of my knowledge in SR and GR, which isn't much, are from reading, studying and searching online myself.
I have seen some definitions that I am not...
Since an object's apparent mass increases as it approaches the speed of light, does it's gravitational forces also increases? (From a stationary observer's point of view)
I don't need equations, I would just like to pose a question which contradicts the above statement (I know I am wrong btw, I want to see where I am going wrong).My understanding of space (not near any gravity and therefore no spacetime curvature) is that a body in motion will continue to move at...
This looks like a physics question but it's not; it's an automotive question. Suppose you had a car at the top of a gently sloped hill, a 5% grade. You start it and put it in neutral or drive and it starts to roll down. You never place your foot on the brake or the accelerator and suppose the...
**My Attempt:** Here, I considered for 2 kg mass the resultant motion is zero, which means it's acceleration (a) would be zero. So, if we consider the Tension force from the 1.5 kg mass to keep 2 kg mass from falling is L, then 2×9.8-L=ma=2× 0 ⇒ L=19.6 N. But where does the tension force from...
a. To find the speed, I need to find the height where the cords first become loose, which is when the cord is 25 m long.
$$h=30-\sqrt{25^2 - 5^2}$$
But the teacher's working is ##h=30-\sqrt{25^2 - 4^2}##
How to get 4?
b. My idea is to use Newton's 2nd law so I draw free body diagram of the...