Change Definition and 1000 Threads

Homework Statement in this question , it's not stated that whether the temperature change from 20°C to -20°C or -20°C to 20°C . I'm confused... Homework EquationsThe Attempt at a Solution I think it should be changing from 20°C to -20°C so delta T = (-20-20) = -40°C , am i right ?

Homework Statement (a)How much heat must be added to a block of 0.120kg of frozen ammonia initially at 100oC to convert it to a gas at 80oC given the following information? (b) assuming this could be done using a reversible process what would be the total entropy change associated with this...

So i am 18 years old , and i just graduated high school with a high score . recently i got accepted into medical school and my parents are pushing me hard to study there . aside from school work , i have been extremely interested in technology , i did some extensive research on programming...

Dear all, The Hamiltonian for a particle in a magnetic field can be written as $$\hat{H} = \frac{1}{2}g\mu_B\textbf{B}\cdot\boldsymbol\sigma$$ where ##\boldsymbol\sigma## are the Pauli matrices. This Hamiltonian is written in the basis of the eigenstates of ##\sigma_z##, but how is it...

Homework Statement in the notes , i was told that ∂A is the resistance of aluminium rod...I'm wondering the change length of steel rod that we can 'see' is ∂ st or ∂T(st) ? Homework EquationsThe Attempt at a Solution I think the change length of steel rod that we can 'see' is ∂ st ?

Why isn't ##\frac{\partial L}{\partial t}\frac{\partial t}{\partial \dot{q_m}}## included in (5.41), given that ##L## could depend on ##t## explicitly?

Okay, best to provide some background here. I am trying to understand the light coming from the LED's over my aquarium. I have blue moon lights I think at about 540nm and 450nm. Oddly enough, when they are on, there is a green tinge to the light. I had assumed that this was because the light...

Homework Statement A rope has an end fixed and the other is passing through a pulley and has a body attached to it. The fondamental frequency of the rope is initially ##f_1=400 Hz##. If the body is then put in water the fondamental frequency of the rope becomes ##f_2=345 Hz##. If the linear...

Homework Statement Find the change in diode voltage if the current changes from 0.1 mA to 10 mA. Ans. 120 mVHomework Equations V2-V1=VTln(I1/I2)The Attempt at a Solution That is all the information given. The only equation I can think to use is the diode voltage/current relationship, but a...

I just have a simple question to ask people of physics since I keep on forgetting to ask my physics teacher. Does changing your direction while in motion affect your velocity? If so why? What forces cause it's velocity to decrease. Assuming that friction is present.(Also would it affect an...

I get two different answers, ##a^2## and ##0.5a^2##, by using two different methods. Which is the correct answer? The family of curve for ##y^2=4u(u-x)## is given by the blue curves, and that for ##y^2=4v(v+x)## is given by the red curves. Method 1: Evaluate the integral ##I## directly in...

Hi there, I was just trying to perform a change of variable on a differential equation as shown below. The original second order ODE is written in terms of a dependent variable ## \theta ## and independent variable ##q##. I have used the expression ## q = \sqrt{\frac{z\tau'}{LT_R}} ## and...

How are the intensity of a sound wave and the Doppler shift of frequency related togheter? That is, if the source or the observer are in relative motion, how does the intensity change? For a sound wave $$I=\frac{1}{2} \rho \omega^2 A^2 c=2 \pi^2 \rho f^2 A^2c$$ (##c## is sound speed, ##\rho##...

Homework Statement A particle with a charge of 2e moves between two points which have a potential difference of 75V. What is the change in potential energy of the particle? Homework Equations U = (75 V)(2e) The Attempt at a Solution [/B] When a particle with charge e moves through a...

Homework Statement An object is moving around the unit circle with parametric equations x(t)=cos(t), y(t)=sin(t), so it's location at time t is P(t)=(cos(t),sin(t)) . Assume 0 < t < π/2. At a given time t, the tangent line to the unit circle at the position P(t) will determine a right triangle...

Question regarding different percentage changes. If I have a monthly rental fee of \$100 in July with a discount of 60%. I will pay \$40. In the month of August the monthly rental fee is \$100 with a discount of 45%. I will pay \$55. My discount has decreased by %15. However my...

Homework Statement The diagram below shows an electrolysis cell which contains 1L of an aqueous 1M copper(II)sulfate solution. If 0.4 moles of electrons pass through the cell, the concentration of copper ions after passage of the charge will be A) 0.4 M B) 0.8 M C) 1.0 M D) 1.2M...

Homework Statement Cu2+ ions react with Fe2+ ions according to the following reaction. Cu2+ + 2Fe2+ --> Cu + 2Fe3+ At equilibrium, the concentration of Cu2+ ions is not changed by the addition of A) Cu2++B) Fe2+C) CuD) Fe3+. Homework EquationsThe Attempt at a Solution I chose A through...

I have Windows 2010 with the corresponding Microsoft Word. Both left-to-right and right-to-left text directions are available upon click (the paragraph sign pointing one way or the other), because I live in a country where both are common. I use both directions, but mostly I use the...

Hey, working on something for a personal project and was wondering if you could point me in the right direction. I have a 47 inch hollow steel tube that I'm going to cut the end 6 inches into a half circle tube . I have a load of 200 lb at the top and am wondering how about I would quickly...

Imagine potential well which in t=0 switches to a different potential well (instantly), like in the picture below. So in negative times the wavefunction density should tend to be localized in the first well, in positive times to be localized in the second well...

The pink spheres cause an acceleration of 1 cm per second squared towards themselves. The aqua spheres cause an acceleration of 2 cm per second towards themselves. All spheres have the same mass. The spheres are attached to a massless, yet mysteriously solid perfectly circular green...

Homework Statement Consider having a battery, its voltage let's say 20 volts. If you connect this battery to a wire. Its resistance is zero. If you precisely measure the voltage at the end of the wire, Would it equal 20 volts or no? Homework Equations dV = I R The Attempt at a Solution Well...

Homework Statement http://imgur.com/Sk6YkIf . You can take Va to be volume of cavity and Di to be density and Vo to be volume of cube and A to be surface area of container and h to be height of liquid column and Vi to be volume of immerser part of cube. Prove if water level will rise or will...

What is the change in entropy of thermodynamic environment if it changes its temperature during the process and the process is not reversible? I'm slightly confused because, on the one side, in that case ##\Delta S_{gas} \neq -\Delta S_{surroundings}##, since ##\Delta S_{universe} >0## but on...

Homework Statement Hi I know my picture has 2 problems, but let's just focus on the first problem parts a and b. So for part a it ask for the final frequency after the ant landed, and part b is the kinetic energy difference. Basically the ant=.01kg, diameter of cylinder is .115m, the weight of...

I'm a 3rd year graduate student doing atomic physics experiment. I was thinking of changing my group to do theoretical biophysics for a few reasons. Did any experimentalist here change to theory? What was the transition like?

Homework Statement You have a ukulele and you change the strings tension so that it becomes tighter. First the frequency was 431 Hz and after we tightened the string the frequency. how much bigger does the force have t be to get that frequency? Homework Equations PA*V^2 = F (P = density, A =...

Does quantum gravity play role inside brain in ever changing perception of time?

I have a problem to understand the de Broglie wavelength. We know that also particles undergo scattering and interference at a double slit. The interference pattern is calculated by the use of the de Broglie wavelength which is defined as lambda = h / p ; p is the momentum of the particle. This...

Given a sample of nitrogen gas (assume ideal gas conditions), the following conditions were observed inside the container. n = 0.75 moles at 253 K, and pressure = 0.5 atm. Then, an ISOTHERMAL IRREVERSIBLE COMPRESSION on the system forced by a constant Pexternal = 10 atm reduced the initial...

I am trying to prove that the above is true when performing the change of variable shown. Here is my attempt: What I am not quite understanding is why they choose to isolate the partial derivative of ##z## on the right side (as opposed to the left) that I have in my last line. This ultimately...

Production function Q(K,L) without equation However partial derivatives are given Partial derivatives: Q(K,L) = (K^2 - KL + L^2)/(K+L) + 4K . ln(K+L) Derivative to K Q(K,L) =( K^2 + L^2) / (K+ L) Dervative to L A. Calculate the derivative in point (10,L) If I am correct...

Homework Statement Calculate ΔH for 2 mols of Nitrogen for the following transformation: 1 bar, 21°C → 200 bar, 21°C Given that molar Cp = 4R 2. The attempt at a solution How am I supposed to find the ΔH? From what I learned, there can only be a change in enthalpy when there's a change in...

Can somebody help me? I am studying Faddeev-Popov trick, following the Peskin and Schroeder's QFT book, but I can't understand one thing. After they inserted the Faddeev-Popov identity, $$I = \int {{\cal D}\alpha \left( x \right)\delta \left( {G\left( {{A^\alpha }} \right)} \right)\det \left(...

If the distance between the plates of a parallel condensor is 4mm and the potential difference is 60 volts . Now if we increase the distance between the plates to 12mm , then Why the electric field does not get decrease , instead of that potential difference between the condensor becomes 180...

Why if a young person like 21 years old with no degrer made a new discovery in theoretical physics like an equation or a theory will not be accepted by people and no one will believe him ? What he should do before to let people accept his discovery ? Can it be accepted if that person was not...

Homework Statement The full range input of a12-bit, successive-approximation type ADC is 1 volt. Determine: a) the maximum input change required to give a one bit change in output of the ADC Homework Equations None The Attempt at a Solution The ADC is 12 bit, so it will produce a...

http://imgur.com/BNQPAQa I'm missing something. Why does x+1/x suddenly become x-1/x2? I get that they moved the x to the top, subtracted the -1-1, but does that exclusively set the fraction negative all on its own ? I've computed it by hand. 1-2 comes out to be 1... So why is it negative... ?

Ok, this will be awkward but i somehow got lost in this thought, For low velocities, the formula for energy boils down to the classical E=1/2m*v^2 So let's say two astronauts A and B are in empty space absent of gravity. B has a jetpack and accelerates to 5m/s which require E=1/2m*v^2=...

I'd like to read some articles, papers, or whatever scientific there is about the prospects and impacts of climate change for professional ground based astronomy and observatory sites. In particular, which locations which are now among the most suitable sites for observatories - especially...

If I add 1402kJ of energy to 1 mol of Nitrogen I will ionize it, as I understand it. So when I ionize it, will it actually change the velocity of the ionized atom? What about the overall temperature of the gas?

So if energy levels, or eV of electrons, do not change with molecular bonding, how are electrons influencing each other.? In glass, when individual atoms of silicon, sodium, and calcium come together, to form glass, the molecular bonding does not change the energy levels of the electrons for...

Homework Statement Hi everyone, this is probably simple but i don't understand why the acceleration in the question is 0.20 m/s2 but in the answer an acceleration of 0.020 m/s2 is used? Can someone please explain why it changes? Thank you! Homework EquationsThe Attempt at a Solution

How is a top gate used to change electron density in 2D semi conductors? I get the principle, you are just shifting the chemical potential by some voltage so that there are more or less electrons in the specific bands. But how is it physically done? Thanks.

if i sucked air out of an oil well after drilling a few feet and closed the hole by any means and continued drilling without allowing air in, will that eliminate change in influx and won't result in a kick? or because i can't suck air completely out so the delta p will be really high?

Hello Community My first post here so excuse me in case i posted in the wrong place. I basically have to write a paper in school about a physics topic. This includes creating graphs with independent and dependant variables and finding the slope. It should be something to complicated but also...

-the electrons to the same shell levels of glass as the microwaves pass through and heat the material, or move electrons in a opaque material to the same energy levels, or shell levels of glass, and transparent liquids, and some plastics. In a microwave the waves traverse food, and heat the food...

I'm a bit stuck on this question (which is homework so hints are more welcome than outright answers). The question is: A very long wire carrying a current I is moving with speed v towards a small circular wire loop of radius r. The long wire is in the plane of the loop and is too long to be...

Homework Statement A uniform magnetic field is perpendicular to the plane of a circular loop of diameter 10 cm formed from wire of diameter 2.5 mm and resistivity 8.5×10-8 Ω·m. At what rate must the magnitude of the magnetic field change to induce a 10 A current in the loop? Homework Equations...