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. HollowSkate

    Engineering Analytical Fluid dynamics

  2. S

    Nonlinear dynamics problem from Strogatz textbook

    For g) how should I argue this claim? To me it seems straight forward because u is linearly related to z. Then so do their derivatives. And by the description of the model, ##\dot z## is linear to y. So it's quite obvious but not sure what I should pay more attention to when I write my proof...
  3. cyap

    Concept of different accelerations on rotations of rigid bodies

    I don't seem to understand the difference of accelerations when a cord is wrapped around cylinders and spheres. What I was taught is that if the cord is wrapped around a cylinder/sphere, the acceleration of the cord and whatever it is connected to will be twice the acceleration of the cylinder...
  4. P

    How Can I Improve My Understanding of Dynamics and Statics of Non-Rigid Bodies?

    Hi, I'm currently looking to improve my understanding (mostly conceptually) on Dynamics (such as colllisions)and Statics of Bodies that aren't perfectly rigid, while considering mass, density, thickness, shape , kinetic energy, momentum and material stiffness/strength/toughness.
  5. M

    Beam boundary condition problem

    In my working, I have drawn a free body diagram of the LHS of the beam, I obtained some equations but after that not sure what I need to do. Usuaully in vibration problems you are given BC's then you plug them into the general solution to obtain the frequency equation. Please can you help me...
  6. MatinSAR

    Rigid body dynamics: A rod with two masses rotates down from a horizontal starting position

    For the rod and the two particles ##x_1## is not zero but we have:$$x_2=x_3=0$$ We start with inertia tensor of the rod: $$ I_{ij} = \int \lambda ( \delta _{ij} \sum_{k} x^2_k -x_i x_j ) dx_1$$ $$ \lambda = constant = M/L $$ Using above equations, we have: $$I_{11} = \dfrac M L \int ( x^2_2...
  7. D

    How to calculate the degrees of freedom of a simple multi-body system?

    I intuitively understand that it has 2 degrees of freedom (rolling without slipping - RWS), but I struggle to formalize this according to the rules of the art: I obtain: 10 - 3 (ground) - (rolling without slipping constraint) = 2 how to precisely calculate the RWS constraint? what formula and...
  8. A

    B How can tension apply torque on a simple pulley?

    Let’s say we have a pulley with some box attached to it, mass of the box is ##m##. We consider rope to be massless and inextensible and pulley to have mass but be frictionless. How can tension apply torque on pulley?
  9. S

    I What drives osmosis? (Statistics or Dynamics?)

    This letter in PhysRevLett describes molecular dynamics simulations to investigate the underlying factors that drive osmosis. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.97.024501 Copy on Internet Archive ...
  10. A

    I Why are the accelerations not equal?

    ##\vec n_2## points to the diagonal top left. The velocity v is a function of t. So for example ##2t^2## and a = dv/dt. Putting the velocity vector into ##\vec n_1## and ##\vec n_2## terms. $$\vec v = v sin\theta \vec n_1 + v cos\theta \vec n_2$$ $$\vec v = -v \vec i$$ $$\vec a = \frac{d\vec...
  11. E

    How Can Derivatives Determine Speed in Physics Problems?

    I have been trying to solve this problem for hours using the mentioned equations but no matter what I do I cannot get the correct answer, that is v = 22.4 m/s. I thought that maybe if I could get an expression where v is a function of time I could solve the problem but I don't know how to do...
  12. superfunnyshark

    Angular Acceleration when accounting n-reference frames

    Hello, I understand the equation that describes the angular accelerator when 3 reference frames are involved is: Now I would like to ask what is the resulting equation when accounting more than 3 reference frames, i.e. when n-reference frames are involved. Thank you.
  13. L

    Stretching of a rotating spring

    TL;DR Summary: Are the k and the w linked? Yesterday I came across this problem: A mass is attached to a spring and the system rotates (one of the spring end is fixed) in an horizontal plane. Given the mass m, the value of k, the length of the spring l_0 and the angular velocity w, compute...
  14. Nova_Chr0n0

    Engineering Dynamics of Rigid Bodies: The Concept of Law of Gravitation

    The questions and relevant formulas/information are attached below: I started by writing the needed values: 2 kN = 2,000 N 6378 km =6378(1000) m 1800 km = 1800(1000)m After converting, I tried solving for the mass using the law of gravitation formula: I decided to replace N as...
  15. E

    How Do Two Rotating Rods Interact?

  16. A

    A planet of mass M and an object of mass m

    HI! I tried to solve this exercise, by assuming that it is an inelastic collision, the planet is spherical, and that the rotation axis is parallel to the z-axis, see the figure attached. (1) before the collision, (2) after the collision.I started by assuming angular momentum conservation, which...
  17. AHSAN MUJTABA

    A Scalar Field Dynamics in Inflation

    I am facing a problem while wanting ##\phi## dynamics in a cubic potential; ##g\phi^{3}##. The equation of motion I get for my case is(this follows from the usual Euler-Lagrange equations for ##\phi## in cosmology--Briefly discussed in Carol's Spacetime Geometry, inflation chapter)...
  18. C

    How to approach dynamics problems?

    TL;DR Summary: How do I approach the setup of this problem? It seems very different than a setup for a kinematics problem I'm self studying first year mechanics and am having a hard time with the following problem (screenshot attached). The example is from Intro to Mechanics by K&K. I'm...
  19. DioMiner

    Why does this not work? Projectile Motion problem for Dynamics Class

    TL;DR Summary: I want to mainly figure out where in the problem solving I went wrong. I understand the correct answer (since I looked it up), but to me, it does not make any sense. I am honestly stumped at this point. Online solutions say that my equation y = 0.5774x-0.003354x^2 should...
  20. S

    Engineering How to Approach the Prandtl Boundary Layer Equation for Steady Laminar Flow?

    I have tried to approach in the following way I am stuck. How should I approach this next.please help
  21. URIA

    How to Determine the Stability Condition in Couette Flow?

    Dear All, I tried to solve the attached question. it's about Couette flow, where the 2 plates move. in fact, I have to find the stability condition. is someone familiar with this and can help? many thanks, uria
  22. B

    Two Particles Connected by Massless Rod: Dynamics Analysis

    Two point-like particles of mass m. The particles are rigidly connected to each other with a mass-less rod of length L. The particles are initially at rest in such a way that one particle is at the origin and the other is at the point (0, L). A point-like particle of mass M collides with a...
  23. Leo Liu

    Engineering [Intro Dynamics] How to obtain v(t) from v(r) in 3D?

    We know that in 1D, we can perform the following steps to obtain velocity in terms of time if the velocity is a function of position: $$v=f(x)$$ $$dt=\frac{dx}{v}$$ $$t_2-t_1=\int_{x_1}^{x_2}\frac{dx}{v}$$ $$x(t)\rightarrow v(t)$$ But I wonder if it is possible to obtain ##\vec v(t)## from...
  24. Idontknowhatimdoing

    Normal force at the top of a vertical loop -- Circular Motion Dynamics

    From the equation for centripetal force, I can see that the centripetal force is proportional to v^2. Does this have something to do with why there is a normal force at the top? Does the velocity of the object require there to be a normal force? If so, why is that the case?
  25. M

    A 4kg mass sits on a frictionless table....

    I got 13N but is that right because apparently, it's wrong Here's my work: F = mg = 2(10) = 20N F = ma a = F/m = 20/4+2 = 20/6 = 10/3 = 3.3m/s^2 T = mg - ma T = (2kg)(10m/s^2) - (2kg)(3.3m/s^2) = 13.4 N I appreciate it! And if I'm wrong could you show how you got your answer? Thanks
  26. N

    Fluid Dynamics Question -- Water flowing through a pipe into two cylinders

    Because my little work project involves fluids I thought this the best topic to post under. I took the route of biological sciences and computer science. This area is out of my league at the moment I'm not sure the amount of time that would be required to get the material applicable to this...
  27. Saalz

    Engineering Applying Physics to Vehicle Dynamics: Do Wheel Number Matter?

    I was modeling the dynamics of a vehicle for a project, and started doubting about the way of applying physics in this particular case. The thing is, I know the torque in the wheels from the torque the electric motor I designed do provide, multiplied by the gearbox ratio. I also know the...
  28. strangerep

    A Interactive Galactic Dynamics Textbook -- Bovy 2022

    Since no one seems to have mentioned this yet... For anyone interested in graduate-level study galactic dynamics, Jo Bovy (Assoc Prof in the Astrophysics Dept at U. Toronto) is in the process of constructing an interactive textbook on the subject, which you can check out at galaxiesbook.org...
  29. R

    Engineering Dynamics Problem with a Driving Force, 2 Wheels, a Spring and a Damper

  30. M

    A Confusion of the scale of contact line dynamics and capillary flow

    I'm having some trouble getting my head around the scale at which capillary flow and contact line dynamics are important. In the simple case of liquid rise in a capillary tube, a smaller tube will allow for greater rise since a larger height is required to achieve an equal weight of the liquid...
  31. S

    I Simple lateral vehicle dynamics model

    I have run into a problem when trying to model a simplified vehicle that has three degrees of freedom – roll, vertical and lateral motions. It is represented by a single mass with two links that model the suspension behaviour. The links connect the tyre-to-ground contact points (tc) to the body...
  32. ElectricVocaloid

    Dynamics problem (force and torque analysis) of a human finger

    I was having trouble with a physics problem (string tension dynamics) In this case I have a model that simulates the phalanges of a human finger. Each phalanx is a block of mass m1, m2 or m3 respectively. And to simplify it, consider the 3 equal masses. These phalanges are linked by joints that...
  33. L

    Direction of friction for three bodies stacked one on top of the other

    I have drawn three free body diagrams, one for each box and then I applied Newton's Second Law after choosing a reference frame rotated clockwise by ##\alpha##, with ##x## pointing south-east and ##y## pointing north-east and I got: ##\begin{cases}m_{1x}: -T+m_1g\sin(\alpha)+F_{fr_{12}}=m_1...
  34. S

    I Exploring the Impact of Non-Stretchy Mat Materials on Trampoline Physics

    Trampolines are in effect coupled springs, with the mat being the much softer spring generally. E.g. On my Acon, when jumping about 1 meter, there is a max cone of depression about 60 cm deep and 1 meter across (1 meter point has a depression of only about 10 cm) At this same point the 160 or...
  35. lindberg

    I Shape Dynamics: How Can It Offer Same Predictions as GR & SR?

    Developers of Shape Dynamics (as Julian Barbour and Tim Koslowski) claim that Shape Dynamics will offer in most cases the same predictions as GR, and implicitly as SR. How can this possibly be true, since they get rid of time altogether and thus of any notion of simultaneity? How would they get...
  36. lindberg

    I Can Shape Dynamics Be Tested Against Quantum Mechanics?

    Shape Dynamics implements nicely Mach's principles. But how well does it fare when it comes to Quantum Mechanics? How can it be experimentally distinguished from other theories?
  37. F

    Intuition on the direction of friction in a rotational dynamics problem

    The figure illustrates the situation. The radii of the larger and smaller discs are 2R and R, respectively. Their masses are M and 2M, respectively (the largst disc has the smallest mass). Also, m=5/4 M, where m is the mass of the suspended object. The pulley is "massless" (negligible moment...
  38. 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...
  39. ROOT0X57B

    How to Calculate the Braking Momentum on a Wheel?

    [Mentor Note -- thread moved from the technical forums to the schoolwork forums] I have a hollow-cylinder wheel model, braked with brake pads located at a distance d of the wheel's center axis. The brake pads have a contact area S. They are also forced towards the wheel with a pressure p. The...
  40. PaxFinnica96

    Engineering Fluid Dynamics: Proof of the Static Pressure Head equation

    I am trying to mathematically prove the Static Pressure Head equation: H = p/ρg How can I prove this equation and thus determine the nature of the relationship between these variables?
  41. V

    Finding tension as a function of distance from the center of rotation

    I'm not too sure how to account for both the mass and the rope at once. I think the following are true for the two individually: For the mass at the end, ## T = m ω^2 L ##, following from ##a = v^2/r##and ##v=ωr##. For the rope, ##dT = ω^2 r dM##, where ##dM = λ dr## and λ is the mass per unit...
  42. mohamed_a

    I Polarizing filter synthesis and dynamics

    I have found a fair amount of sources for studying polarized light but I haven't found sources discussing synthesis of polarizers in detail along with mechanistic discussion.
  43. V

    I Non-Newtonian description of an accelerated object

    Hello, everyone! In the first few chapters of Physics 1, there is the description of motion, and the computation of the acceleration vector as being the sum of the rate of change of velocity, with the division of linear velocity squared by the instant radius of curvature: The above equation...
  44. D

    How Does Colatitude Affect the Direction of Coriolis Force?

    So I don't understand "due north from a position at colatitude ##\theta## " , whether how I translate it... I keep getting that direction should be radial...(toward Earth CM) This is my work: Thank you so much!
  45. Shreya

    Buckets on a pulley - Dynamics Problem

    A) I am not sure if initial velocity means the initial velocity of the putty. If then, it should be 10m/s. But the answer given is 10/7 m/s B) i have solved this part correctly C) the answer should be 86J Please be kind to help me
  46. K

    I Modified Newtonian Dynamics + dark matter sterile neutrinos or PBH?

    what about Modified Newtonian Dynamics + dark matter both right and both correct Are sterile neutrinos consistent with clusters, the CMB and MOND? Garry W. Angus arXiv:0805.4014 [ If no sterile neutrinos then Modified Newtonian Dynamics + primordial black holes Primordial Black Holes...
  47. Z

    Exploring the Benefits of Planar Multibody Dynamics in Mechanical Engineering

    Hello I am reading the book : " Planar Multybody dynamics, Formulation, Programming and Application" An interesting lecture , however is it worthwhile studying these methods for kinematic and dynamic analysis of mechanical mechanisms? I mean There are many softwares on the market which make...
  48. L

    Engineering How to Combine Signals for High Dynamic Range?

    hello I am working on a project concerning a measurement technique which consists of adding two signals from different sensors in order to obtain a signal with very high dynamics. and I would like you to help me because I saw your interventions concerning this system. I don't know yet if this is...
  49. A

    Data sources for Vehicle Dynamics Model validation?

    Hello all, I have written a VDM for my Masters thesis, unfortunately, since I am from a discipline other than mechanical engineering I don't have access to reliable validation material or a way to produce it (moreover, we don't have an actual vehicle testing lab/area at the U that I know of)...
  50. G

    Olympiad dynamics problem with 3 masses and a pulley

    Hello all, this is an adaptation of a question i saw some time ago (can't find the original now). There are two forces acting on two masses both 1kg. The masses are joined by an inextendable rope and going over a frictionless pulley of negigible mass. In blue I have written in some working out...
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