# What is System dynamics: Definition and 27 Discussions

System dynamics (SD) is an approach to understanding the nonlinear behaviour of complex systems over time using stocks, flows, internal feedback loops, table functions and time delays.

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1. ### Choosing what consists of a "system" in Newton's laws of motion

The question is solved in a single step by taking the blocks as a system and using conservation of linear momentum in the horizontal direction as there is no net force acting in the horizontal direction. Conserving the momentum we get, m x v + M x 0 = (m+M)v', so,,v' = mv/(m +M).where v' is the...
2. ### Solar System Dynamics page at NASA/JPL

Stumbled across this and found it interesting. Solar System Dynamics pages at JPL (Jet Propulsion Lab)/NASA. Has Bodies, Orbits, Physical Data, Tools, etc. https://ssd.jpl.nasa.gov/?site_map Cheers, Tom
3. ### Potential Energy for "stone + field" physical system

Consider the classical scenario a stone falling in the Earth gravitational field. Classically we attach a Potential Energy to the stone and using the law of conservation of (mechanical) energy we are able to evaluate the dynamic of the falling stone. This model assume a stone in a "external"...
4. ### Studying How to approach ME System Dynamics problems?

In Summary: I have a test Friday in modeling mass-spring-pulley systems, and I'm struggling to tie everything together. We're using the textbook System Dynamics 3rd Edition by William Palm III, and while it does a great job describing the individual components of each system, it does a crappy...
5. ### Equation of Motion of a System of Springs (System Dynamics)

I'm having trouble understanding the forces involved when defining the equation of motion for this particular problem. So... I've seen the answer for the eq. of motion worked two different ways. The first way involves combining the spring series into Keq = K1⋅K2/(K1+K2). The answer, plugging...
6. ### Solving Equal Force Chain System Dynamics

Homework Statement Imagine exactly same two bodies (same mass, same surface/friction etc) are attached with a string/spring and they suddenly start pulling towards each other with equal force. I can imagine they will move towards the center. If there is a chain (with defined number; not...
7. ### Understanding the Equivalence of Two Mechanical Systems

I cannot understand the mechanical systems in the picture. In the picture a) how can f is scattered equally to M, K1, K2, B1 and B2 ? Where do you know this? How can two systems be equivalent of each other? In the picture (b) if f is applied, how can the force on M is Ma, a is acceleration...
8. ### I N-body codes for planetary system dynamics

A while back I did research in planetary system dynamics that involved the code package Mercury. Unfortunately, I found that Mercury would occasionally crash for no reason or give nonsensical results. This happened for a small subset of initial conditions and while I spent some time debugging...
9. ### Engineering Alternative for Ogata System Dynamics?

Because the section on frequency domain analysis (vibrations) is hurting my brain... Are there any alternatives to this book that may be a little less abstract? Thanks, Mac
10. ### Sun Orbits Center of Mass w/ Jupiter & Earth: How To Calculate?

I know that if I have a two-body system, the sun and the earth, then the common centre of mass is orbited every 365 days. What about if I add another planet in, say jupiter? Does the sun still orbit the centre of mass every 365 days? With two bodies, their orbital period about the centre of mass...
11. ### Finding the Hamiltonian of this system

Homework Statement I am asked to find the Hamiltonian of a system with the following Lagrangian: ##L=\frac{m}{2}[l^2\dot\theta^2+\dot{\tilde{y}}^2+2l\dot{\tilde{y}}\dot{\theta}\sin{\theta}]-mg[\tilde{y}-l\cos{\theta}]## Homework Equations ##H = \dot{q_i}\frac{\partial L}{\partial...
12. ### Struggling to Understand Pulley System Dynamics

Homework Statement it is Problem 3.30. Homework Equations I am not sure how to sum the forces about each consecutive pulley I have been at this for 4 hours now. It is sad I can solve the DE questions and not this. The Attempt at a Solution I had the first pulley at the top as (where y is...
13. ### Engineering Systems Modeling Question (First order thermal circuit)

Homework Statement I have a problem with understanding the thermal circuit I attached to this thread. Please help. It's a Thermal circuit of a computer CPU that needs to be simplified to have just 2 lumped capacitances and resitances. How would one go about doing that? along with the equations?
14. ### Aceleration & tension in a system involving pulley

1. Homework Statement I am stuck on this problem involving tension, acceleration of a system, friction and a pulley. I have an idea of how to find the acceleration of the system neglecting the mass of the pulley, but it is not the solution. How does adding a frictionless pulley in the system...
15. ### System Dynamics (Fluid system)

Hello friends I am from Saudi Arabia . I have a project in System Dynamics course . The Project is to design a fluid system that Qout should be 0.95 Mass flow rate enter the system.see the attached file for more information . Please if someone can give me a hint or the procedure how to start...
16. ### Modeling & Simulation in Physics: ZHAW Aviatik Course

The importance of modeling and simulation for understanding physics is a central question of didactics. System dynamics is a promising method to achieve this goal. This method is applied at the Zurich University for Applied Sciences (ZHAW...
17. ### Solar System Dynamics, advice for a intern.

Hello Physics Forums Community, I have completed ODE, 3 semesters of intro Calc, 3 semesters of intro physics, taking linear now. I have recently gotten the opportunity to work on little projects with a professor of astrophysics at a university. On the first meeting, the professor handed me...
18. ### Troubleshooting System Dynamics Problems - Expert Help Needed!"

Hi folks! My system dynamics teacher gave us a couple of assignments to work out, there is one though that I can't seem to work out properly. Now I am aware that this is maybe not the correct part of the forum, but I didn't know where else to put it. I would love to see one of you guys...
19. ### Why Are T1 and TL Negative in Gear Train Dynamics?

Homework Statement See attachment. Homework Equations The Attempt at a Solution Equations (1) and (2) describe this gear train system. I'm confused about them. For (1): If I rewrite it (∑F=0 format) I get: T-T1-Jθ''-Bθ' = 0 The figure clearly shows θ1 positive spinning...
20. ### System Dynamics: A Qualitative Understanding

I did read some of the posts on the topic. However, I just want to check my qualitative understanding without employing too much mathematical dynamics. If anyone has some feedback, this would be much appreciated. The System. A spring hangs vertically. There is a mass attached to it...
21. ### System dynamics but with math - guidance needed

A couple of months ago, in-between jobs, I was doing some light research work at Cornell and sitting in on some classes (hiding behind a Big Red hoodie) when a graduate student offhandedly introduced the class to system dynamics and continued rambling on. I knew immediately that that was what I...
22. ### Compressed Air System Dynamics: Calculating Pressure Drop & Cv

I want to work out the dynamics of a compressed air system consisting of a filter/regulator unit some spool valves and a rotary actuator with all the associated fittings. Essentially I have a 2" nominal bore compressed air line at roughly 7.5 bar, I have a system which feeds off this air main...
23. ### Any good book that can teach System Dynamics? (details inside)

Hey guys, I need a book that can teach me system dynamics, here is what they teach in the course: Linear time invariant system, impulse response function, operator, convolution, system characterization, solution of linear ordinary differential equations, Laplace transform and its...
24. ### Solving Pulley System Dynamics: Acceleration & Tension

Two masses are attached to a massless, frictionless pulley as shown. (image is attached) A) Find the acceleration of the two masses and the tension of the rope connecting them. B) Now the top surface is replaced with one which has a coefficient of kinetic friction of 0.2. FInd the...
25. ### Solving a System Dynamics Problem: Fishing Boat Displacement over Time

Homework Statement The problem: A fishing boat weighing 147,150 N is towed by a much larger ship. The tow cable is linearly elastic and elongates 0.0278 m for each 1000 N of tension in it. The wave and viscous drag on the fishing boat can be assumed to be linearly proportional to its...
26. ### Effect of dark matter on solar system dynamics

Dark matter plays a significant role on the relation between orbital radius and velocity of stars within galaxies. Does it, however, have a theoretically calculable and eventually measurable effect on planets, like those of our solar system?
27. ### System dynamics step/ramp formula

HI all, I'm taking a basic system dynamics course and I'm either having a problem with a concept or just with the notation. I think the easiest way explain the problem I'm having is with an example ( see jpeg). If I have f(t) = 0 when t <= a and [(bt)/(a+b)] - b when t>a I would have the...