System Definition and 1000 Threads

I calculated as attached and got it right. However, I just wonder why we can't use conservation of energy as the question has already specified 'frictionless', meaning no energy loss and energy distributed to the rotation only.

I calculate in this way : Angular Momentum = I W = [ ( 1/12 ML^2 + m(L/2)^2 ] (V/ L/2) = [ 1/12 ML^2 + 1/4 mL^2 ] 2V/L = 2VL/4 [ M/3 + M] but can not find a matching answer. Why?

So all of the ice melts and I am guessing it then warms some so Q=mL+mc(change in T) for the water that cools down Q=mc(change in T) Q_cold = -Q_hot so -mc(Tf - Ti) = mL+mc(Tf - Ti) My issue is that I have 2 unknowns. I don't know the specific heat capacity of water and I don't know the...

Summary:: How to form an automatic billing system through Bluetooth and mobile phones? For commercial purposes, how can my system automatically signal, calculate the billing value and actually perform the billing or transfer the transaction from a credit or debit card or a bank account? [Note...

I think it is quite simple as an exercise, following the two relevant equations, but at the beginning I find myself stuck in going to identify the lagrangian for a relativistic system of non-interacting particles. For a free relativistic particle I know that lagrangian is...

Hi, Could you please help me with the queries below? Question 1: Do you think that the free-body diagram for M1 correct? It looks fine except that, I think, the arrow for M_{1}\frac{d^{2}}{dt^{2}}x_{1} should point downward. Question 2: Similarly, I think that the free-body diagram for M2 is...

I am doing a cosmological work and I need to run a code form this github page https://github.com/ja-vazquez/SimpleMC I download the whole repository as .zip file and I inserted into my desktop. Then I opened it through vs code and this is how it looks like The problem is that, when I run...

In college I wasn't as fortunate as wealthier students and actually had to work in college. As a result of having less time study, the wealthy kids generally speaking did better, they had more time to study. Should the students with better grades and 4.0 GPA take away 0.5 from their GPA and...

Dear All, I'm a french professional photographer working on Still Life and Architecture. As a long time and personnal project I'm working on a 3D printed/Laser cut analog camera that will shoot 6x4.5 frames. In the end it will be some kind of rangefinder with integrated electronic light...

I have my set of differential equations which is dx/dt = -2x, dy/dt=-y+x2, with the initial conditions x(0)=x0 and y(0)=y0. I'm a little confused about how to approach this problem. I thought at first I would differentiate both sides of dx/dt = -2x in order to get d2x/dt2 = -2, and then I would...

Hi I want to know a little more about learning operating system. My grandson told me he is taking a class in operating system and the teacher use C and C++ mostly. He and his friends are in trouble because his school is Java based, none of them really know C++ and C. Is Operating system...

Please see question attached. I am really stuck on this.

I have no idea about a possible solution, please help me :)

AIUI, the early universe, after the Great Recombination, was a fairly, but not absolute, isotropic cloud of mostly H, with some He. Eventually regions of the cloud coalesced into stars, and if the mass was big enough, the temperature & pressure in the star core was sufficient enough for H in...

Let me start off by saying that I realize it would be much easier to haul a fridge up stairs into the man cave , but what fun is that. I have this novel , totally unnecessary project in mind. I want to make a beer delivery system. Something like you would see in a bank drive threw. My man cave...

So first I made an equation representing the forces Fnet=kx-12.8v a=1/m(kx-12.8v). Now I am not really sure how to get w from this. I could argue the mass is at its max amplitude when a=0, but that wouldn't help me find w. If I say x(t)=kx-12.8v, then 1/m would be w^2, but this isn't right...

Hi, On a driving force graph ##y = displacement (m)## and ##x = time## where the external force start at t = 0 and the system is in equilibrium at x=0, it's easy to find the driving frequency. $$F = \frac{\omega}{2\pi}, \omega = \frac{2\pi}{T}$$ and we can get ##T## easily with the steady...

I'm given this code to plot the system for task 1 where my teacher have used some random numbers just to show us how the code can be used: The code makes a plot that is given below: So my professor just gave us this code and plot without saying anything more. All the students in the class...

Five electrons are in a two-dimensional square potential energy well with sides of length L. The potential energy is infinite at the sides and zero inside. The single-particle energies are given by (h^2/8mL^2) (nx^2+ ny^2) where nx and ny are integers. The energy of the first excited state of...

https://www.physicsforums.com/threads/is-the-universe-a-closed-system.620503/ Hello. I was looking back at this thread from 2012 and, to be honest, I'm a bit confused. Quoting Drakkith... To our knowledge it is. At minimum you could count the observable universe as a closed system because...

A recent thread by @coolcantalope was accidentally deleted by a Mentor (I won't say which one...), so to restore it we had to use the cached version from Yahoo.com. Below are the posts and replies from that thread. The cached 2-page thread can be found by searching on the thread title, and is...

Could directed energy fundamentals be used in active confinement by hybridizing the heating system with directed energy. I'm sure I'm wrong in this because I only have my high school diploma.

There are 3 different strings in this system. The one pulling P, the one pulling F and the one pulling a pulley. Since the questions says they're ferried across before hitting mast or deck, I'm assuming that they are not stationary. g is gravitational acceleration. P will move twice as fast...

I'll be focusing on mainly trying to find a way to solve part a, as I don't actually know how to account for the tilt. When they said degrees arc I assume they're just saying degrees, so I found the distance of Earth to sirius to be around 1.50 x 10^8 km(radius of the earth), because of the...

Hi guys, I managed to solve this problem just by "rewriting" the first equation of the system as ##t=f(x)## and then substituting that in the second ##y=f(t)## equation, ending(of course) up with the sought ##f(x,y)## function. The problem here is I didn't really understand what I have done and...

I am looking for a textbook or handbook on optical system design. I would prefer one that actually derives equations rather than just slapping down rules of thumb, although I would take the latter. My problem is that I've done a ton of bench top optic setups, but my skills are kind of capped at...

What is the method of calculating the diameter of a solar system knowing each of its planets distance to the star? Is it a matter of doubling the distance of the furthest planet? What about when a solar system has more than one star?

The other day when I solved a spring mass damper system in Matlab, I was curious how in olden days would have people solved the equation. We all know the 2nd order differential equation of the system: However if I know the time, damping coefficient, stiffness and mass, will I be able to find...

My book uses ##1/2m_1v_{1c}^2+1/2m_2v_{2c}^2=1/2m_1v_{1c}'^2+1/2m_2v_{2c}'^2## to show that the angles of deflection of the collision between two particles are the same in the centre of mass frame. However, I am doubtful that one can apply the conservation of energy to a "moving" system because...

I'm struggling with calculating the flow rate for an oxygen system. There is a pressurised cylinder. This then joins onto a pressure reducer. Then travels down a length of pipe which branches off to 4 exits there is no restrictions on the exits it just goes to atmospheric pressure. I am yet to...

The first thing I do is making the argumented matrix: Then I try to rearrange to make the row echelon form. But maybe that's what confusses me the most. I have tried different ways of doing it, for example changing the order of the equations. I always end up with ##k+number## expression in...

Let's assume a binary system with an inclination angle ##i## (angle between the orbital plane and line of sight). Then, according to this source - equations (128) and (129) - for the amplitudes of the tensor polarization modes ("plus": ##+## and "cross": ##\times## polarization) I could write...

Let ##L## be the state space of two identical/indistinguishable particles. Let ##L \otimes L## be the state space of the combined system formed by both particle. If the particles were distinguishable, ##LxL## would have four mutually orthogonal states: ## |\phi\rangle|\phi\rangle...

Hello! Assume we have a simple harmonic oscillator potential, in 3D (say created by some electric fields, such as a Paul trap) and inside it we have a 2 level system in the excited state (say an ion in which we care only about 2 levels, for example the lowest 2). The translational energy of the...

I am designing a hydro power system that will tie into an off grid solar system. I will be using a 48v carbon AGM battery bank. Will be using the Sol-Ark 12kw inverter/charger, which has 2 built in MPPT charge controllers for solar. Assume the hydro power will be around 5 kw potential, and...

Hello, I found an old thread related to this question but it doesn't look correct to me so was looking for some guidance. I have equated Qo = (Q2+Q1*G) / (1+H*G) I did this by rearranging Qo=Q2+G(Q1-Q0*H) I then went on to the calculations and found before step disturbance: Qo=...

Summary:: We want to find explicit functions ##g(y,t)## and ##f(y,t)## satisfying the following system of differential equations. I attached a very similar solved example. Given the following system of differential equations (assuming ##y \neq 0##) \begin{equation*} -y\partial_t \left(...

I have to study the solutions of the following system of three equations and three unknowns upon variation of parameters k and h. ix1+kx2-x3 = 1+i (k+i)x1+(1-i)x2-(ik-1)x3 = h kx1+(4+2i)x2-(k-3-3i)x3 = 1-i Obviously i is the imaginary unit. And as stated k and h are the parameters . I can't...

I honeslty don't quite know how to start. It seems like the Hooke's coefficent k is independent of the answer to this problem. I would also appreciate any clue of expressing the condition when "balls will collide again". The fact that all balls can keep moving make this rather difficult. It...

I've tried to show b) by using the sine Fourier series on ##[0,2a]##, to get ##g_k = \Sigma_{n=0}^{2a} \sqrt\frac{2}{a} Sin(q_k x)## Therefore ##\sqrt\frac{2}{a} = \frac{1}{a} \int_0^{2a} Sin(q_kx)g_k dx## These are equal therefore it is an orthonomal basis. I'm not sure if this is correct so...

This looks like a classical setup but I can't find a solution. We can calculate the energy of the system by looking at the work done by the gravity and the spring. But how do we divide the energy between the kinetic energy of the pulley and the rotation of the pulley?

[Thread moved from a technical forum, so no Homework Template is shown] A controller is required to monitor the natural illumination of a sports stadium and, when the ambient light is below a pre-set level, to switch on external lighting. The system is required to be of high integrity, and...

I attempted using f = 1/(2pi x sqrt l/g) For Earth I found the value of length to be 0.0276m. Then I substituted the value in the equation, putting (1/3)g instead of g, to find the value of f in Mars. My answer is C. I am confused. Please help me.

Summary:: need help with solution group of Homogeneous system Is the solution group of the system A^3X = 0 , Is equal to the solution group of the system AX = 0 If this is true you will prove it, if not give a counterexample. thank you.

In thinking about temperature stratification of air: I assume that in a truly closed system with no heat inputs, air would NOT stratify by temperature. On the other hand, a heat source introduced in a closed container would generate stratification while it was generating heat (and following for...

I would to know if I'm solving system differential equation by elimination correctly. Could somebody check my sample task and tell if something is wrong?

My hypothesis: A sequence with the gravitational waves detected, sent by modulating radio waves, could be received and used by other intelligent beings to find the corresponding sequence within their records and then compare it to calculate our spacetime position in relation to theirs. As...

Maybe my question is naive and due to my not deep enough knowledge of particle physics. I imagine we entangle two particles on Earth and then send one on spaceship going from Earth - two coordinate frames moving in relation to one another. Moments of simultaneity are different for them. When...

My first step was to calculate Torques acting on system, I found 3, one given(external): a)torque produced by point mass: (m2)grcos(θ)=(m2)gr b)torque produced by spring krsin(θ)rcos(θ)=kr2θ c)external torque τ_o(t)=10sin(20t) I also calculated moments of inertia I=m1r2+(1/2)m1∗r2 then I...

$\tiny{311.1.3.19}$ find h and k such that the system has, no solution (parallel) ,unique solution (intersection) , many solutions (same line) $\begin{array}{rrr} x_1+hx_2&=2&(1)\\ 4x_2+8x_2&=k&(2) \end{array}$