Dynamics Definition and 1000 Threads

General Dynamics Corporation (GD) is an American publicly traded, aerospace and defense corporation headquartered in Reston, Virginia. As of 2020, it was the third-largest defense contractor in the United States, and the third-largest in the world, by sales. The company is a Fortune 100 company, and was ranked No. 83 in 2020.Formed in 1954 with the merger of submarine manufacturer Electric Boat and aircraft manufacturer Canadair, the corporation today consists of ten subsidiary companies with operations in 45 countries. The company’s products include Gulfstream business jets, Virginia- and Columbia-class nuclear-powered submarines, Arleigh Burke-class guided-missile destroyers, M1 Abrams tanks and Stryker armored fighting vehicles.
In 2020, General Dynamics had worldwide sales of $37.9 billion and a workforce of more than 100,000 full-time employees. The current chairman and chief executive officer (CEO) is Phebe Novakovic.

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  1. L

    Maxwell eqs. - integral formulation in dynamics

    The integral formulation of Maxwell equations, for example the one called "Gauss' theorem", see the first equation here: https://en.wikipedia.org/wiki/Maxwell's_equations is still valid in dynamics, with rapidly varying sources? We know that a rapidly varying charge here gives a flux of an...
  2. Buzz Bloom

    I Questions regarding dark matter dynamics

    I recall reading somewhere (I can't remember where) that there is astronomical evidence that dark matter has different densities in different parts of the relatively near parts of the observable universe. Q1. Is this correct? If so, can someone please post a link to a relevant article? The...
  3. A

    A Fluid Dynamics Problem with Confusing Results

    Hi all, I encountered a fairly straightforward problem involving fluid dynamics, but the result I got is very confusing and I seem not to understand where I got wrong. This is the question: A rectangular flat-bottom barge with a bottom area A=50 m2A=50~\text{m}^2A=50 m2 is loaded so that the...
  4. P

    Does the moment of inertia stay the same in different positions?

    Good evening, good people of PF. I have a fairly simple question. Please see the attached drawing. My question is this: does the moment of inertia change from position one to position two (as the weight is rotating around a center line). In essence, does it maintain the same moment of inertia...
  5. ramzerimar

    How is the moment of inertia of airplanes measured?

    I know it's possible to use a trifilar pendulum to extract information on moments of inertia by measuring the period of oscillation. I've seen this test being executed on small aircraft, like in this video. But I wonder how do is the momement of inertia calculated on big aircraft, like a Boeing...
  6. Narasoma

    Introduction To Constrained Dynamics: Resources & Sources

    I need a brief introduction to constrained dynamics. Any article, paper or books will help. If you know sources related to that matter, please tell me...
  7. O

    Work/Energy in the introduction to dynamics

    An introductory course in rigid body dynamics for mechanical engineers introduces kinematics, then kinetis and then work/energy. Can I ask for your opinions? Is this necessary? I can see the need to discuss work/energy to understand Hamilton's Principle. But is there any reason to labor...
  8. O

    Why does the Principle of Virtual Work work without higher math?

    The last chapter of most introductory textbooks on STATICS introduces VIRTUAL WORK. It is rarely taught (I studied the syllabi of colleagues). I understand the Principle of Virtual Work, having researched and studied the Calculus of Variations, Hamilton's Principle, the Lagrangian and related...
  9. E

    In which direction a spherical particle moves under torque?

    Consider a small rigid spherical particle of radius a, fully immersed in a viscous incompressible Newtonian fluid of shear viscosity η above a hard-wall with stick (no-slip) boundary conditions, located at the plane z = 0. A constant positive (external) torque Tx is applied on the particle. My...
  10. O

    2 Conveyors with different speeds

    (mentor note: moved here from a non-homework thread) Hello I am trying to find the time it will take for a parcel to pass over one conveyor belt The conveyor on the right is Conveyor A The conveyor on the left is Conveyor B they both have a length of 700mm Conveyor A has a constant speed of...
  11. M

    Solve Dynamics Questions: Get Help and Advice

    Mod note: Thread moved from technical section so no homework template shown. Hello there, I am working on a dynamics question, but I am not sure how to tackle it since my teacher has not really taught this topic well. I would like some advice on how to start the question off and the method...
  12. F

    2 methods same answer dynamics

    In this dynamics MIT open coarseware they are teaching this method where I sum forces on first mass, sum forces on second mass and then sum of torques = change in angular momentum. The way I originally learned it was just to look at it and do this : MX1''=-KX1 - BX1' + M2G/L*(X2-X1)...
  13. N

    I Classical v. quantum dynamics: Is spin the key difference?

    I'm interested in understanding the key physical differences between classical and quantum dynamics. I understand that spin (intrinsic angular momentum) is one major physical difference.* So I wonder whether all else flows from this? Or are there other major (unrelated) physical differences...
  14. Eclair_de_XII

    Courses In your experience, is E+M harder than dynamics?

    Just curious on what everyone considers to be the harder calculus-based class in college.
  15. B

    Convert second order of diff. equations to first order

    Homework Statement I have this set of equation: My''+Cy'+Ky=0 but C=0 M is a matrix consist of {(-m) (0)/( -1/12mb^2) (-1/12mb^3)} and K is a matrix of {(-K1-K2) (-K2b)/ ((K1b-K2b)/(2)) (-K2b^2/2)} and y is a coordinate system which is (x1,θ) Now i have to convert these...
  16. T

    Multiphase Flow in Fluid Dynamics - Energy Coupling

    Hello, I have a general question regarding energy coupling in multi phase flow. My question comes is based on the text from this book...
  17. Sirsh

    MATLAB Issues Replicating Simulink Model within MATLAB (2DOF)

    Hey all, I've been trying to debug a model I've created of a 4DOF geared system within Simulink by reproducing the results in MATLAB going from a 2DOF upwards to verify the dynamics are acting correctly. At the moment I am purely trying to model the stiffness between two gears, my equations...
  18. S

    Fluid Dynamics Homework: Solving for Velocity Components at Stagnation Point"

    Homework Statement Homework Equations The Attempt at a Solution I tried a few different things, they all involve finding u and v components of velocity. I know the stagnation point is at y = 0. I also know that at stagnation u = v = 0. If I get the velocity magnitude and set it equal...
  19. S

    Exploring Fluid Dynamics: Homework Statement and Equations

    Homework Statement Homework Equations The Attempt at a Solution I don't even know where to start. I don't understand the question.
  20. A

    Explicit dynamics (LS-DYNA export) -- How to export a Time waveform?

    I am doing guided wave simulation in ANSYS workbench. I applied a load (tone-burst signal) on the model and I ran the simulation successfully. Now, I want to extract the time waveform. Does anybody have any idea?
  21. O

    A Tangent Bundle: Why It's Important

    Good Morning All: I am now understanding a bit -- just a bit: still struggling - about the tangent bundle. But I have no idea WHY this is important. As I understand, at every point on a manifold (or, more appropriately: at the coordinates placed on a manifold by a mapping), we study the union...
  22. S

    Fluid Dynamics: Pressure Field - Vector or Scalar? | Homework Question

    Homework Statement This is not so much a homework problem but a question I have on the subject while studying. I have a terrible teacher who is contradicting my textbook constantly and I really want to learn this. Is a pressure field vector or scalar? If given the velocity components, is...
  23. A

    Find mass of load that falls off truck

    Homework Statement A truck with a heavy load has a total mass of 7500 kg. It is climbing a 15 degree incline at a steady 15 m/s when, unfortunately, the poorly secured load falls off! Immediately after losing the load, the truck begins to accelerate at 1.5 m/s 2 . What was the mass of the load...
  24. C

    Hilbert Dynamics in choosing position in BM/MWI

    In General Relativity. Gravity is caused by curvature of spacetime. In MWI and Bohmian Mechanics.. the position observable and position preferred basis is chosen. There must be a non-zero energy or some kind of dynamics that would lock the particular Hilbert space vectors into those special...
  25. Sirsh

    4DOF Spur Gear System - Eigenvalues not corresponding with the Eqns?

    Hi there, I am modelling a four degree of freedom system which is the dynamics of two spur gears in mesh, having two rotational and two translation degrees of freedom, respectively, a diagram exhibiting the system can be seen below. I have derived the equations of motion (EOM) and...
  26. S

    Air-Track Carts & Spring (Energy)

    Homework Statement The air-track carts in the figure(Figure 1) are sliding to the right at 2.0 m/s. The spring between them has a spring constant of 140 N/m and is compressed 4.1 cm. The carts slide past a flame that burns through the string holding them together. What is the final speed of...
  27. S

    Dynamics Questions // Elastic Collision with different Vo

    Homework Statement [/B] A 2.3 kg object traveling at 6.1 m/s collides head-on with a 3.5 kg object traveling in the opposite direction at 4.8 m/s. If the collisions is perfectly elastic, what is the final speed of the 2.3 kg object? Homework Equations Conservation of Energy: 1/2 m*vi^2 = 1/2...
  28. R

    Question about friction? Dynamics

    Homework Statement This is the problem http://imgur.com/a/1XFlt 2. Homework Equations This is the given FBD http://imgur.com/a/CURqA 3. The Attempt at a Solution Now the car should have a tendency to slip down the ramp thus causing the frictional force to oppose this motion. But the...
  29. C

    Dynamics question.... where did this formula come from?

    < Mentor Note -- thread moved to HH from the New Member Introduction forum, so no HH Template is shown > Hi there, I found a thread from 2004 that perfectly answered my homework question here, but I don't understand how the person who responded came up with the answer. I would have just...
  30. anony123

    Why does adding more pulleys increase the force on a block?

    Hello, First of all, I'm new to this forum and to not know whether this thread is in the right place or not. If not, feel free to replace it. I'm in my first year of university, studying industrial engineering. On a test I got the following image: The red square is a block with a specific...
  31. R

    Dynamics Question -- packages discharged from a conveyor belt

    Homework Statement A series of small packages, each with a mass of 4 kg, are discharged from a conveyor belt as shown. Assume that the coefficient of static friction between each package and the conveyor belt is 0.4. Determine the force exerted by the belt on a package just after it has passed...
  32. E

    Dynamics question related to conservation of string

    Homework Statement http://tinypic.com/r/10f5ni8/9 http://[PLAIN]http://i66.tinypic.com/10f5ni8.png Homework Equations I have a problem understanding this problem. It asks for the velocity of block A when block B is moved 300mm/s to the right. The equation for the cord length is given as...
  33. J

    I Acceleration w/o Velocity Change: Gravity Ques

    If acceleration involves a change in velocity - dv/dt, what velocity is changing for an object at rest with gravitational force? Example - an apple on a table, mg down = the normal force ma up, but neither a nor g seem to involve a dv? the forces involved do not involve changing any...
  34. jerry wickey

    How can Bernoulli's principle help explain pressure changes in fluid dynamics?

    Can someone smarter than I, please express p1 and p2 in terms of f, or v and r? The pump pushes out water at f rate which creates velocity v in the bigger pipe. When the water comes to the restriction velocity increases while flow rate is conserved. Bernouli tells us that the change in...
  35. Hepth

    Dynamics of pumping fluid into a cylinder with an air hole?

    I should be able to do this, but its been a while and maybe I'm making this more difficult that it should be. Assume you have a cylinder nearly sealed but with an outlet hole at the top. I want to pump a fluid into the canister, pushing the air out of the hole, and time how long it takes. The...
  36. R

    Optimal Shape for a Submersible Object with 360 Degree Maneuverability

    For a given submersible object that has 360 directional maneuverability, what would be an ideal shape for that object? Sphere? **360 degree directional maneuverability meaning jets strategically placed around the object for propulsion, without rotating the object
  37. L

    Equations of Motion: Constrained Hybrid Dynamics

    Hi all, I've tried to figure this out for some time without luck. Hope you might be able to give some input. I've implemented a model-based dynamics software in MATLAB based on the works of Roy Featherstone's Springer book "Rigid Body Dynamics Algorithms". So, I have the EoM of an...
  38. Astronuc

    Update on Tectonic Plate Dynamics

    This caught my attention the other day, and I don't yet have time to review/explore the topic. A discovery about the movement of tectonic plates will have scientists rewriting (or update?) textbooks http://www.businessinsider.com/what-moves-tectonic-plates-2017-1 20 TW is pretty impressive...
  39. Patrick Jago

    Where Does the Energy Go in an Electric High Pressure Water Motor or Pump?

    In an electrical high pressure water motor or pump what is the main cause of energy loss. Originally I was thinking along the lines of 1st heat/electrical losses in motor. 2nd Friction of the water in pipes. 3rd noise. But I'm torn between the first 2 ? Tho
  40. H

    Rotational Dynamics Designing a Propeller Velocity/Acceleration

    Homework Statement You are asked to design an airplane propleller to turn at 2400 rpm. The forward airspeed of the plane is to be 75.0 m/s, and the speed of the tips of the propeller blades through the air must not exceed 270 m/s. What is the maximum radius the propeller can have? With this...
  41. U

    Dynamics -- Velocity of a Block in a system of Pulleys

    Hey guys, I have been a long time lurker here but this problem has eluded me for a few hours now and my frustration at not being able to figure out what it is I am missing prompted me to finally pull the trigger on making an account here. I hope the way I wrote everything out is clear to...
  42. RMalt

    Manometer Reading using Fluid Dynamics

    Homework Statement so I have been working on this problem : Diameter1 at wide end: 8cm || V1 = 1.56m/s Diameter2 at narrow end: 3cm || V2 = 11.094m/s Force exerted on plate = 87N Find the manometer reading Picture below: Homework Equations P1+(1/2 ρv1^2)=P2+(1/2 ρv2^2) 1 − 2 = (2 −1)ℎThe...
  43. RMalt

    Evaluate Problems using fluid dynamics

    I have a diagram similar to the following. Water entering the larger end is at 20degreesC. The larger end has a diameter of 8cm and Area 50.26cm2. The small side has a diameter of 3cm and Area 7.0685cm2. The water jet exerts a force of 87N on a flat plate at an unknown distance. Assuming no...
  44. X

    Scaling The Solar System By A Factor ##\alpha##

    I am given the solution to the first part of the problem, however not the second part - would appreciate for someone to double check my work! Cheers. 1. Homework Statement If a scale model of the solar system is made using materials of the same respective average density as the sun and...
  45. F

    Courses Dynamics through physics or mechanical engineering?

    Which is better? To study dynamics through physics or through mechanical engineering? What is the difference really? A book from MIT OCW classical mechanics 2 : Florian, Scheck. Mechanics: From Newton’s Laws to Deterministic Chaos. 3rd ed. https://www.amazon.com/dp/3540655581/?tag=pfamazon01-20...
  46. JoeStrout

    How to simulate rotational stability of multiple parts?

    I've written a space colony simulation game called High Frontier. It correctly simulates rotational stability when most of the mass is dominated by a single large spinning part. For example, a squat cylinder will be stable, but a long cylinder will end up tumbling end over end, as shown...
  47. Alettix

    Energy conservation in superball collision

    Homework Statement There are two elastic "superballs" of mass M and m placed on top of each other with a smal distance. The lighter ball of mass m is on top of the bigger ball of mass M. The balls are released from a height h and have velocity u when they hit the ground. Prove that the top ball...
  48. O

    Work, energy, impulse, momentum

    In most "introduction to dynamics" textbooks, why do we teach work and energy? Consider a textbook like Hibbeler's Dynamics: Chapter 1: kinematics of particles Chapter 2: kinetics of particles Chapter 3: Work Energy Chapter 4, Impuse and Momentum AND THEN IT REPEATS FOR BODIES Now, I...
  49. R

    Dynamics: Cannon ball and the moving gun

    https://postimg.org/image/z96a0jn8b/ https://postimg.org/image/z96a0jn8b/ link to image (bcs the feature doesn't work): https://postimg.org/image/z96a0jn8b/ 1. Homework Statement A cannon (mass m_c) is standing on the ground before it fires a cannon ball (mass m_b). At the time t_0=0. the...
  50. ikihi

    Mass and pulley system (Rotational Dynamics)

    Homework Statement Consider a pulley with a mass-less cord attached to its edge. The rope hangs a distance of d= 2.50 m below the bottom of the pulley. Attached to the end of this cord is a block with mass 3.00 kg. There is also an electric motor attached to the pulley which supplies a torque...
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