Constant Definition and 1000 Threads

Here is a question that might be somewhat more philosophical than this community cares for. If so, I apologize in advance. Are there any reputable theories as to why the speed of light is constant? I know that it is an empirical fact and therefore that it does not need to be proven. But on...

Try as I may, I can't figure out how to even phrase the following in a way to google it, so I apologize in advance if it is a trivial question, I am no physicist. What I am trying to discern is if there are very very small shifts in the perceived charge of an atom over very very small amounts...

How would I go about finding temperature distribution in a thin square plate during the the first few milliseconds (or actually a fraction of a millisecond) after t=0s. Initial temperature distribution throughout the plate is known, there is heat flux to one side = Qinj, while heat flux from all...

Homework Statement I don't get how you can use x and p instead of delta x and p in Heisenberg's principle. Also why is it just h bar? Isn't it supposed to be h bar/2? Problem 2-iv Homework Equations delta x* delta p >= h bar/2 The Attempt at a Solution I tried to deal with this problem but I...

Homework Statement A boat is sailing starting from x = 200m. When interpreting x(position) vs. t(time) graph for this boat with math models x = -20t + 200(t<=10), Is it right to say "The boat is approaching to the origin" ? (When t <= 10) Homework Equations x = -20t + 200(t<=10) The...

My GF and I got into a petty argument about pressure washers. She believes that the constant back-pressure you feel holding a pressure wand increases the closer you hold it to a wall (for example). Where as I believe that if the wand had a constant psi, with outward pressure, wanting to force...

Dear friends, Does anyone know how we can solve the TOV equations for a non constant density? In all the references, I just saw the solution for a constant density. Thanks in advance for the help :)

Hello everyone. I am having some problem with dark energy and the cosmological constant. The cosmological constant is a proposed form of dark energy. Alright, now the cosmological constant is is estimated by cosmologists to on the order of 10^-26 kilograms per cubic meters. But the density of...

HI Guys .. I really need some help on this ... I need to manufacture(mix) a liquid that 'displays' as UV light if that's the correct term. any ideas where I could start ? I have limited chemicals knowledge :/

Homework Statement Determine Kepler's third-law constant Ku for Uranus using the data for the first four moons. Homework Equations [/B] (r)^3/(T)^2 = K Data: Moon #1 (Ophelia) r=5.38 x 10^4 km T=0.375 Earth Days The Attempt at a Solution [/B] I know the question asks for the K constant...

Homework Statement Problem: [/B] Given the mass spring system solve for k1 The natural frequency wn = 10 s-1 k1=2k2 m=1kg Homework Equations wn=(k/m).5 The Attempt at a Solution solve for k1 m x w2n =2.5k1 k1 = 40 N/mNote: I calculate 40 N/m and the solution states 250 N/m. I think I...

In one book of Susskind I found the following claim and I wanted to ask for its basis. Susskind says that each kind of boson gives positive contribution to the cosmological constant (the lighter, the better). Each kind of fermion gives negative contribution to the cosmological constant. Thus...

Hi, A capacitor has both its terminals connected together using a wire in a rather lengthy circular fashion, hence acting as a significant inductance. If the area encircled by this 'circuit' is subjected to a linearly rising magnetic field (B=k x t) where k is a constant, the emf induced -due...

Homework Statement Consider a free particle, initially with a well defined momentum ##p_0##, whose wave function is well approximated by a plane wave. At ##t=0##, the particle is localized in a region ##-\frac{a}{2}\leq x \leq\frac{a}{2}##, so that its wave function is...

Pictured below was a problem shown in class with solution. I didn't have time to ask the professor a question about the last step involving an additive constant. V is potential energy, re=Earth radius and z is distance from Earth's surface. What is an additive constant, and how does it...

Hi all, I'm trying to come up with velocity equations for a multi-enzymatic system and came across this velocity equation. Does anyone recognize this equation? There was no citation or derivation and the variables were not explained. This is my guess: P, Q, A, B are concentrations of some...

I would like to clear out my understanding of gas compressor. If it is moving at constant RPM, is it mean that it can only allow same volumetric flow rate all the time? So the power will remain constant too, (P=VI) then voltage and current will varies. My investigation is to find why there is...

I am trying to model the maximum performance of a linear actuator assembly and create a flexible excel tool for calculating other systems in the future. The actuators are simple ball screws driven through a gearbox by a motor, typically BLDC so the torque is relatively constant over most of the...

If c_v is the specific heat at constant volume, authors substitute this into the first law as follows: c_v d\theta + pdv = dq How can one deduce that equation for any case? Since the specific heat at constant volume is used, the equation would be valid only where there is no expansion i.e...

Why is the dielectric constant smaller in few-layer materials than in bulk materials?

A simple harmonic oscillator consists of a block of mass 45 g attached to a spring of spring constant 240 N/m, oscillating on a frictionless surface. If the block is displaced 3.5 cm from its equilibrium position and released so that its initial velocity is zero, what is the phase constant, φ ...

Dear forum I am working with thermal radiation. This is the specific formula: P = σ ⋅ A ⋅ T4 P = emitted effect (W, J/s) σ = Stefan-Boltzmann constant (5,67 ⋅ 10-8) A = area of object (m2) T = temperature of object (K) How can I get to know the...

What is the effect in quantum if Planck constant is zero? Here are some points that I could think of: if Planck constant is zero, the Heisenberg Uncertainty Principles will become zero, therefore either momentum or position of a particle can be known exactly. if Planck constant is zero, both...

Suppose that there's a wheel. A constant torque is applied to the wheel from the central axis. What is the relationship between the amount of force received by each particle on the wheel in relation to the distance each particle is away from the axis?

I read a article now and It claims he found the cause of cosmological constant.Is that true ? The idea is actually good...

In a discharging battery, do current and voltage decrease over time? if so how does the battery accomplish the same amount of work over the course of its discharge with a lesser voltage or current?

If the speed of light is constant regardless of the state of motion of the source, then doesn't this imply that it is possible to calculate the velocity of a reference frame by measuring the time it takes for light to traverse some known distance in that frame. For instance if our frame is...

Hi there! I'm having some trouble understanding Hubble's Law and Constant and would be grateful for some help. So Hubble's Law shows that the most distant galaxies have the greatest red-shift, as they are moving away from us fastest. This shows that all galaxies are moving away from each other...

In the constant volume gas thermometer, T (°c)=[P(T)-P(f)]×100/[P(b)-P(f)] (P(T) means gas pressure at T°c P(b) and P(f) for the water's boiling point and freezing point) Is it right?

Homework Statement Why is the horizontal velocity for a projectile constant? I understand it physically, since the vertical and horizontal velocities aren't related and don't affect each other, g will only affect V_y and neglect V_x, so it's constant. But maths-wise, isn't V_x =...

[Note from mentor: this thread was originally posted in a non-homework forum, therefore it does not use the homework template.] ------------------------------- So I've been asked to prove that in a harmonic function where a(t)+w2r(t)=0 that (1) v(t).v(t)+w2r(t).r(t)=constant scalar and...

Homework Statement A person is standing over a well and drops a rock. After 2.4 seconds he hears a rock splashing into the water. Take the speed of sound to be 300m/s and calculate the depth of the well. Homework Equations x=v/t for constant velocity x=1/2at^2 for accelerated motion The...

Homework Statement Jupiter's moon Io has active volcanoes (in fact, it is the most volcanically active body in the solar system) that eject material as high as 300 km (or even higher) above the surface. Io has a mass of 8.94 × 1022 kg and a radius of 1815 km . Ignore any variation in gravity...

is mass of light constant

Hello, If I take a DC motor and put it in generator mode, what will happen if I connect a resistance at the wire ending of the DC motor? Will the motor turn slower compared to when the electric wire of the motor is connected to nothing? What effect will the resistance have on the current...

I know that the power of an engine is equal to (rpm*torque)/ 9.54 (SI units). But does this mean that an engine when turned on is outputting the same amount of energy per unit time, every time ? . What happens when we press the gas pedal, does the power output increases? When i drive my car...

Homework Statement How would i go about finding the electric field and potential difference when there is a constant charge density between the capacitor rather than a vacuum? Homework Equations int E dot dA = Qencl/epsilon0 V ab = int E dot dl The Attempt at a Solution to be honest I am not...

Has there been any recent changes in the G constant value?

Hi all, I'm new here on Physics Forums and can't wait to delve into some juicy topics! I have a very practical problem that I need help with. I am doing a home project where I want to move a platform on wheels (loaded to a maximum of 70kg) in a 1.5m long straight line across the floor at a...

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > Could anyone please correct me if I have any mistake in the following question? It's very important for me to know if I am doing it correctly. 1) "Michelle, a technician at a spring...

Homework Statement At the beginning of a 10 sec. interval your position is measured to be 80 ft East with respect to a reference object. At the end of the 10 sec. interval your position is measured to be 965 ft East with respect to the same reference object. Determine your velocity at t = 3.45...

While studying Faraday rotation (linear magneto-optic rotation) I came across a fact that faraday rotation can be enhanced. Verdet constant which depends on the wavelength can be enhanced as change in refractive index with change in wavelength is maximum near resonant light. Now if the incident...

Hello,Lets say I start off with constant acceleration of 1 m/s^2, and I want to evaluate it at 3 seconds. a = 1. a(3) = 1 then, since at=v, v(t) = at = 1(3) = 3m/s then I can work backward v/t = a = 3/3 = 1 then, since vt = d d(t) = vt = 3(3) = 9 then I can work backward d/t= v =...

Homework Statement A rock is released from rest from the top of a very high cliff, and accelerates downward at g. Approximately how far does the rock travel in the first 7 seconds of its free-fall? (Assume no air friction.) Homework Equations X=Xo+VoT+1/2AT^2 The Attempt at a Solution I...

I just wonder if there were any serious (and peer reviewed published, to be in line with guidelines) theory, which had proposed some link between speed of light in vacuum constant and between gravitational constant G. For example a calculation of speed of light based on G. Tried google search...

Generally pressure in a liquid changes with height at which we measure. But still blood pressure remains almost same throughout the body. How is this possible?

Using the standard equation of a circle x^2 + y^2 = r^2, I took the first and second derivatives and obtained -x/y and -r^2/y^3 , respectively. I understand that the slope is going to be different at each point along the circle, but what does not make sense to me is that the rate of change of...

Gas pressure in a closed chamber at constant temperature will last forever, unless leaking or chemical reactions occur. Examples are methane in underground gas reservoirs that are hundreds of thousands of years old. Gases stored in bottles. Pressure comes from the gas atoms (with velocity)...

The way I see it, a constant supply of power, say from the engine in a car to its wheels, will cause it to accelerate at a decreasing rate because the kinetic energy the power supplies is proportional to the velocity squared. That makes sense because going faster will cause the car to encounter...

I am trying to wrap my brain around the idea of the cosmological constant, and how it gives the result of an accelerating universe. I have read different explanations for it, and in some it gives me the impression that it is an actual physical force, pushing everything away from everything...