What is System: Definition and 1000 Discussions

A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpose and expressed in its functioning. Systems are the subjects of study of systems theory.

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  1. M

    Obtain the two incongruent solutions modulo 210 of the system

    Consider the following system of congruences: ## 2x\equiv 3\pmod {5} ## ## 4x\equiv 2\pmod {6} ## ## 3x\equiv 2\pmod {7} ##. Then \begin{align*} &2x\equiv 3\pmod {5}\implies 6x\equiv 9\pmod {5}\implies x\equiv 4\pmod {5}\\ &4x\equiv 2\pmod {6}\implies 2x\equiv 1\pmod {3}\\ &3x\equiv 2\pmod...
  2. A

    Can this system of inequalities be solved for x?

    Summary: Can these two equations be solved for x like a system of linear inequalities, and how? ##x- 2y \le 54## ##x + y \ge 93## We start with ##x- 2y \le 54## ##x + y \ge 93## Multiplying the second equation by 2, we have ##2x + 2y \ge 184##. We cannot seem to cancel the y out with the...
  3. M

    Find the solutions of the following system of congruences

    Consider the following system of congruences: ## 5x+3y\equiv 1\pmod {7} ## ## 3x+2y\equiv 4\pmod {7} ##. Then \begin{align*} &5x+3y\equiv 1\pmod {7}\implies 15x+9y\equiv 3\pmod {7}\\ &3x+2y\equiv 4\pmod {7}\implies 15x+10y\equiv 20\pmod {7}.\\ \end{align*} Observe that ## [15x+10y\equiv 20\pmod...
  4. M

    Find the solutions of the system of congruences

    Consider the system of congruences: ## 3x+4y\equiv 5\pmod {13} ## ## 2x+5y\equiv 7\pmod {13} ##. Then \begin{align*} &3x+4y\equiv 5\pmod {13}\implies 6x+8y\equiv 10\pmod {13}\\ &2x+5y\equiv 7\pmod {13}\implies 6x+15y\equiv 21\pmod {13}.\\ \end{align*} Observe that ## [6x+15y\equiv 21\pmod...
  5. D

    Can a Hydraulic Motor Determine Torque and RPM for a Two Chain Sprocket System?

    [Mentor Note -- postprocessed attached image for clarity] Hello! Looking for a formula(s) on how I can determine the Torque and RPM needed on the chain (by hydraulic motor) to move the load in the illustration at 240 inches per minute. The load will vary, so I won’t ever really need to push...
  6. E

    B Displacement of Hanging Mass - Simple Pulley System

    I'm having some kind of mental block. If I extend ##l_x## by ##\delta## ,I expect the hanging mass to move ##\frac{ \delta}{2}##. I can't figure out how this is the case from the constraint: $$ l_x+l_1=C $$ ##C## is an arbitrary length I keep getting that ##l_1## changes by ##\delta##, but...
  7. Rikudo

    Rocket Escape Velocity from the Earth-Sun system

    I have a difficulty when making the energy-conservation-equation for the second step. When making the equation, we need to know the exact position (measured from the sun) of the rocket after it is freed from the Earth gravitation. But, where exactly does the rocket free from Earth...
  8. M

    I Water bath and water vapor + air mixture in a closed system

    Hello, At my work I came up with the following question: Say we have a vacuum chamber. Inside the vacuum chamber we have at the bottom a water bath. The rest of the chamber is filled with a air and water vapor mixture. The whole system is placed in a room, is at room temperature and is in...
  9. L

    Current through ring in solenoid-ring system

    The following is my solution to this problem; I would appreciate some feedback, especially on part (b), which I have found the most challenging. Thanks. (a) Using Ampere's Law I get ##B=\mu_0 n i_1## where ##i_1## is the current through the solenoid, and since ##\phi=Li_1##, where ##L## is the...
  10. S

    Acceleration of system related to rolling motion and pulley

    There is no friction mentioned by the question so I assume the plane is frictionless but can the sphere roll without slipping if there is no friction? This is my attempt: Equation of translation motion of object A (assuming A moves upwards): TA - WA sin θ = mA . aCOM (A) TA = mA . aCOM (A) + WA...
  11. hxtasy

    Gerotor pump, will it work in a closed system without air?

    just hypothetical question, First off I am not very knowledgeable in pumps. Let's say you have a pump to pump fluid, i don't think the type matters, self priming as I understand it creates a vacuum with the air in the system to pull the fluid towards the gear pumps. I'm wondering what happens...
  12. chwala

    Solve the following linear system

    Find the problem below with the solution indicated; The text approach is much clear to me... My way of tackling the problem is as follows; using echelon form (row reduction method) \begin{bmatrix} 1 & 1 & 2 & -5 &3\\ 2 & 5 & -1 & -9&-3 \\ 2 & 1 & -1 & 3&-11\\ 1& -3 & 2 & 7&-5...
  13. R

    Heat Transfer Through a Two Material System due to a Light Source

    I have been given the task of modeling the heat transfer from a light source of known power into a system consisting of two connected materials. I must find the temperature change in the bottom surface. The two materials are initially in thermal equilibrium with the surroundings. My first...
  14. S

    Car-Car System: Energy Conservation?

    this is an easy problem but would it be possible to consider car-car system. What I did on paper was carsystem and because they have the same properties(mass en speed) multiply by ##2## solution for car-car-earth system I assume is the following if it is possible? solution for car-car: law or...
  15. TheJP78

    Building a Solar System simulation with python

    Hey'all. First of all, I'm not fluent in English, so forgive me for the spelling mistakes. So, I'm trying to make a simulation of a solar system using python 3.9. It's not complicated, but my teacher wants me to do it using the Basic Verlet method, and that's what is bugging me. He told me do do...
  16. Ranku

    I Mass distribution in a celestial system

    If two sets of objects, of similar size but different mass, were to be part of a rotating celestial system, how differently would they be distributed? Would the distribution of the lower-mass objects be more spread out, while the higher-mass objects would be concentrated toward the centre?
  17. S

    What is considered the "System" here? (conservation of energy problem)

    So in this picture friction is also assumed, but if we assume friction as an energy don't we need to consider the system to be earth, roller-coaster car, roller-coaster itself(due to friction force)? I actually still had this question from a previous coverage of this material lol... I just...
  18. S

    I "A system tries to minimize total potential energy"

    While reading this thread on Stack Exchange... https://physics.stackexchange.com/questions/113092/why-does-a-system-try-to-minimize-potential-energy ... a question came to mind : - Say an object is launched away from Earth at a velocity greater than the escape velocity. This system will not end...
  19. L

    A spring, disk and pulley system

    (a) By setting up a coordinate system with the x-axis pointing to the right and the y-axis pointing downward we have ##\begin{cases}-kx_{eq}+T_1+F_{s}=0\\ -RF_{s}+rT_1=0\\ r_p (T_2-T_1)=0\\ -T_2+mg=0\end{cases}\Rightarrow x_{eq}=\frac{mg}{k}\left(1+\frac{r}{R}\right)## which coincides with the...
  20. M

    A Model the pressure of a zero-gravity simple fluid system

    Hi PF! A circular cylinder contains an inviscid liquid, which is softly disturbed (i.e. velocities are small). There are no body forces, which implies the equilibrium free surface is that of a spherical cap with radius ##R## (see figure A). Inviscid implies we can assume potential flow, such...
  21. M

    I Does Space Curvature Account for Gravity Between Individual Atoms?

    I am trying to come to terms with the two concepts of gravity, direct attraction between bodies (say dust even) and attribution to the curvature of space (time) Looking at a physical sea coast I can envisage how every instance of the mass gravitational interactions of individual atoms or smaller...
  22. M

    B Conservation of Momentum for system of particles

    We know that if we take two particles and assume no external force is applied then by Newtons third law total momentum gets conserved after collision. If we take three particles and there is collision between them and no external force then the momentum is again conserved for each pair like in...
  23. J

    I am grappling with a gravity fed water system and have questions

    How did you find PF?: Google I have an off grid home that uses a spring fed gravity flow water system. The spring is about 200 feet up a steep mountain- and very low flow. The pipe run starts at 2” pvc and eventually is 1.5” pvc. Once down the hill the water flows about 1 mile down an old...
  24. Astronuc

    B Evolution of planetary system around a white dwarf

    An article came up on Phys.org about a white dwarf drawing in material from the planetary system surrounding it. Is this the ultimate fate of our solar system? https://phys.org/news/2022-06-dead-star-cannibalism-planetary-far-reaching.html...
  25. N

    How to Determine the Sign of the Doppler Shift?

    answer:
  26. V

    Determining $L_{o}$: Finding Angular Momentum of System

    I think the the time given doesn't matter since no torque is acting on the system, but not sure. Therefore, all we need is to determine the angular momentum about the axis passing through O and perpendicular to the plane of disk. This will involve finding the moment of inertia of smaller disk...
  27. O

    MHB Partially Decoupled System with 3 variables

    Hello! I have the following initial value problem: \[ x' = x + 2y + 3z \] \[ y' = 4y + 5z \] \[ z' = 6z \] All I'm looking to do is find the general solution to this system, and as long as I'm doing this correctly I have these answers: \[ y(t) = K_2e^{4t} + \tfrac{5K_1}{2}e^{6t} \] \[...
  28. LCSphysicist

    Solving Cylinder+Bead System Problem | Hello.

    Hello. I am having some difficulties regarding this problem. I am not sure, actually, how to relate the angle rotated by the cylinder ##\phi## and the angle drawed by the bead itself ##\theta##. I have been thinking in two alternatives: a) The first one is that, since there are no friction...
  29. MarkTheQuark

    Spring-mass system with a pendulum using Lagrangian dynamics

    I'm stuck in a problem of a spring mass system with a pendulum attached to it as showed in the figure below: My goal is to find the movement equation for the mass, using Lagrangian dynamics. If the spring moves, the wire will move the same amount. Therefore, we can write the x and y position...
  30. sanderalan

    Energy recovered from a regenerative braking system

    Start velocity is 100 km/h, at 1.5g for 0.5 seconds the end velocity will be 73,52 km/h. So the energy can be calculated if the mass is present, but it is not given. Is there a way to calculate the regenerated energy with the given information?
  31. M

    Partition Function for system with 3 energy levels

    I determined the partition function of the particle A, B and C. C should be the same as B. I then considered the situation, where all particles are in the system at the same time, and drew a diagram of all possible arrangements: The grey boxes are the different partitions, given that we...
  32. LCSphysicist

    Work done by gas expanding into a cylinder+piston system

    I will summarize briefly my reasoning for both letters, since the answer is immediately after that: A) The work is quasi-static, and the pressure is approximatelly constant and equal to the atmospheric pressure, so the works is $$W = -p\int dV = -p_{0} (V_{0}-V)$$ B) The work is fast, fast...
  33. K

    I Questions about a System in Equilibrium

    Pathria, Statistical mechanics, pg 93 "We consider the given system ##A## as immersed in a large reservoir ##A'##, with which it can exchange both energy and particles. After some time has elapsed, the system and the reservoir are supposed to attain a state of mutual equilibrium. Then...
  34. jtbell

    New cross-platform password-less authentication system in the works

    How Apple, Google, and Microsoft will kill passwords and phishing in one stroke (Ars Technica) The key acronym is FIDO (Fast IDentity Online). As I understand it, basically, you authenticate yourself to a website or service on your phone using a fingerprint or facial recognition as can already...
  35. Samama Fahim

    Finding Probability of Two-Identical-Particle System in a Given State

    Problem: A system contains two identical spinless particles. The one particle states are spanned by an orthonormal system ##|\phi_k>##. Suppose that particle states are ##|\phi_i>## and ##|\phi_j>## (##i \neq j##). (a) Find the probability of finding the particle in the state ##|\xi>## and...
  36. P

    Escape velocity of solar system

    I'm pretty confused by this but I have a few thoughts. Since the sun takes up most of the mass of the solar system, I was thinking maybe I'm really looking for the escape velocity of the sun? So I would use the mass of the sun for M and the radius of the sun for r. My other thought was to add up...
  37. SR_0301

    I Statement about torque in a system of particles

    Hello guys, I’m studying Newton’s Mechanics at the first year of engineering, and I would like to ask one question about torque. In my book I found this statement ‘’ Given a system of particles, it’s always possible to determine a pair of forces which torque is indipedent from the pole chosen...
  38. J

    B How is efficiency defined in rocket propulsion?

    Whicle has 4 wheels, inside is oval closed room with fan that blow inside air to the wing. Wing produce difference in static pressure in direction of travel. Will vehicle move forward or not? If I look just at pressure difference at wing, vehicle will move forward but I know from Newton 3 law...
  39. S

    Period of spring-mass system and a pendulum inside a lift

    Based on the formulas, variable ##m , k, L,g## do not change so my answer is (a) but it is not correct. Why? Thanks
  40. J

    I How is target superheat table generated for R22 HVAC system

    It seems the practice is to enter the table with evaporator air intake wetbulb temp and condenser ambient temp. I'm trying to understand the theory that translates these readings into the proper target superheat. Thanks
  41. Trysse

    B: Calculate the distance between two points without using a coordinate system

    Dear all, the following problem is not a home-work problem. I have come up with this question for myself. Nevertheless, I am stuck and need your help. The question is: Can I calculate the distance between points A and B from this information? And if yes, how? I think it should be possible...
  42. ace130

    Frequency Response Problem for given system

    Hello, I am given an exercise in which I need to answer some questions, for this given system : y(n)=1/3[x(n)+x(n-1)] 1/ find the impulse response h(n), then H(n) 2/ calculate the magnitude ||H(n)|| and tell the nature of the filter 3/ calculate Fc which is cutoff frequency when Fe=8Khz , and...
  43. B

    Euler-Lagrange equation: pulley system

    ##m_{A} = 3 kg## ##m_{B} = 2 kg## ##y_{A} + y_{B} = c \Leftrightarrow y_{A} = c - y_{B}##, where c is a constant. ##\Rightarrow \dot{y_{A}} = -\dot{y_{B}}## The Lagrangian: $$L = T - V$$ ##T =\frac{1}{2}m_{A}\dot{y_{B}}^{2} + \frac{1}{2}m_{B}\dot{y_{B}}^{2}## ##V = m_{A}g(c - y_{B}) +...
  44. J

    Find the Potential energy of a system of charges

    There are six pairs. three turn out to be negative and three turn out to be positive (3q^2 - 3q^2) which nets zero when you add them together with the equation. But zero was the incorrect answer. Did I do something wrong? Thank you
  45. L

    Stargazing Is There a Reliable Supernova Alert System?

    I was wondering if there are any reliable Supernova alert systems, where they notify me as soon as a supernova happens. I have a 20 inch telescope, and I have SNEWS installed. However, since SNEWS is only a detection for nearby galaxies, I was wondering if there is any alert system for...
  46. VVS2000

    I Damping in a coupled pendulum system

    http://www.cts.iitkgp.ac.in/Phy_1st/Lab_WorkBook/CoupledPendula.pdf This is similar to the experiment which I did
  47. A

    Leg suspended in a traction system

    A leg is suspended in a traction system, as shown in the attached image. (a) Which pulley in the figure is used to calculate the force exerted on the foot? (b) What is the tension in the rope? Here T is the tension, wleg is the weight of the leg, and w is the weight of the load that provides the...
  48. L

    Pulley system to balance the weight of a person

    Since we are dealing with an ideal rope, we have that ##T_1=T_2=T_3=F and T_2+T_3=2F=(m+m_p)g\Leftrightarrow F=\frac{m+m_p}{2}g.## ##T_4=3F+(m+m_p+M_p)g=\frac{3}{2}(m+m_p)g+(m+m_p+M_p)g=(\frac{5}{2}m+\frac{5}{2}m_p+M_p)g## and ##T_5=mg-2F.## Is this correct? If not, I woould appreciate a brief...
  49. Dario56

    Extraction Flash Calculation - 4 Component and 2 Phase System

    I am performing extraction flash calculations for 4 component and 2 phase system. For anyone somewhat shaky with what extraction flash calculation is; extraction is performed, feed composition is known and we are calculating compositions of both phases at equilibrium, mole fraction of every...
  50. S

    I How to calculate the HP/torque required to rotate a dual sprocket/chain system?

    Hi, I am trying to determine the HP motor/torque that will be required to rotate the sprocket/chain system in the image below from a resting position. The sprockets will be at rest, rotate 5 degrees, come to a stop for 5 minutes, and then rotate again 5 degrees, repeated. The speed of...
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