What is Dynamics: Definition and 1000 Discussions

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. C

    Mechanics- Dynamics of particle moving in a straight line questions

    Homework Statement 1. A small pebble of mass 50g is dropped into a pond and falls vertically through it with an acceleration of 2.8ms^-2. Assuming that the water produces a constant resistance, find its magnitude. 2. A lift of mass 500kg is lowered or raised by means of a metal cable...
  2. A

    Rotation dynamics, dealing with impulse and oscillation

    Homework Statement A homogene rod with length "l" is placed vertically, and a nail is stabbed on the top of the rod (now the rod has an axis). And then an impulse is given on the rod with the separation between the impulse given to the rod's axis is "d". Earth gravitational acc is represented...
  3. A

    Rotation dynamics, dealing with impulse and oscillation

    A homogene rod with length "l" is placed vertically, and a nail is stabbed on the top of the rod (now the rod has an axis). And then an impulse is given on the rod with the separation between the impulse given to the rod's axis is "d". Earth gravitational acc is represented as g, the mass of the...
  4. A

    Air Pressure in Elementary Dynamics Problems

    Hello all, I was thinking about situations in introductory courses or textbooks where pressure or buoyant forces are suddenly introduced in situations where they become relevant which lead me to think about the consequences of neglected said forces in more elementary problems. I'm curious as...
  5. C

    Rotational dynamics problem

    Homework Statement a) A 1.5 kg frog sits at rest on top of a solid disk. The disk's mass is 4 kg, its radius is 1.25 m, and it rotates on a frictionless axle. The frog jumps from the disk at 3.7 m/s at an angle of 50°. Find the angular momentum of the frog about the axle as it leaves the disk...
  6. L

    MHB Another one of dynamics

    two masses, each of 400 kg, connect with a thin cord and pull up a plane inclined 30 °, as shown in Figure The coefficient of friction between M and the, inclined plane is 0.5; the coefficient of friction between M2 and the piano is negligible. (a) determine the acceleration of the system and...
  7. E

    Rotational Dynamics Problem

    Homework Statement A hard drive consists of a rigid circular platter (or disk) of radius 0.05 m and thickness 0.002 m. In normal operating conditions, the hard drive spins at 7200 rotations per minute. The read/write head is a light metallic element that floats just above the platter and both...
  8. S

    Relativistic Dynamics problem

    Homework Statement A particle of mass m and kinetic energy K strikes and combines with a stationary particle of mass 2m, producing a single composite particle of mass √17 m. Find the value of K Homework Equations E= γmc^2 , p = λmv The Attempt at a Solution I have tried many times...
  9. A

    Velocity on a hill Kinematics Problem with Dynamics

    In the sport of luge, a competitor slides on a sled down a 500-m long straight ice track inclined at 20o to the horizontal. Her initial speed is 2.0 m s-1. The coefficient of dynamic friction between the sled and the ice is 0.050. Neglect air resistance. What is her acceleration? What is her...
  10. X

    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...
  11. N

    Solving Fluid Dynamics Pressure at Different Speeds

    Homework Statement If the pressure reading of your Pitot tube is 17.0 mm Hg at a speed of 150 km/h, what will it be at 700 km/h at the same altitude? Homework Equations The only eq I could think if is p = p2+ 1/2 density (v2^2 - v1^2) But I don't know the density The Attempt at...
  12. G

    Which one is more harder Dynamics Or Kinematics ?

    Hi everyone; I'm a ME student who just finished Dynamics course and I did really good. I've finished also statics course it was not easy, I faced some difficulties. So, the next semester I'll do "Kinematics and dynamics of machinery" course and I'm so worry. Is it real that Kinematics is...
  13. I

    Very basic fluid statics and dynamics question

    consider the image on the drawing at the top (above the yellow arrow) if i had some non-compressible fluid enclosed in a pipe like container that looped back in on itself (as shown in figure), and if the container was non-elastic, when i rotate this container filled with fluid such that...
  14. S

    Fluid dynamics, Pipe Flow, Hagen Poiseuille, Darcy's equation

    Homework Statement A water injection line is made from smooth capillary tubing with inside diameter D = 25.0 mm . If the length of the pipe is 0.75 m and assuming laminar flow is present up to Re = 2000, find (i) the maximum average velocity at which the flow is laminar (ii) the pressure...
  15. L

    What is the step response of a filling chamber with changing air pressure?

    Homework Statement This is a experimental problem that I am trying to model: I have an air source with constant pressure P connected with a small chamber (cylinder). The chamber has initial internal pressure P_0 and as time t goes, the pressure in the chamber raises to P. So, find the step...
  16. T

    Weak Field Dynamics Homework: Equations of Motion

    Homework Statement The metric for a given particle traveling in the presence of a gravitational field is g_{\mu\nu}=\eta_{\mu\nu}+h_{\mu\nu}, where \eta_{\mu\nu} is the Minkowski metric, h_{00}=-2\phi (\phi the Newtonian gravitational potential); h_{i0}=0; and h_{ij}=-2\phi\delta_{ij}. Units...
  17. J

    Multi-body dynamics sim software

    Hi all, I've been looking around for a simple software to test mechanical assemblies, typically ones using a motor to drive some gear or pulley system. This is for garage scale projects, nothing really big or really small. Ideally it would be something that would be able to give me the...
  18. U

    Dynamics Moments - Linear Algebra / Cross Product

    Some background: I am self studying dynamics and I have encountered a fundamental problem with either my understanding of linear algebra, or I am just plain dumb. So, I print screened the page of the book we're on. Now let me try to reduce some ambiguity in my question, I have a general...
  19. C

    Dynamics- collision of cars problem

    The problem is like this Assume both cars A and B are intially traveling to the right at 98 ft/s. Car A is tailgating leaving very little room between car A and car B. At that instant driver of car B notices a n accident and starts to break witha deceleration of 2o ft/s^2. By the time the...
  20. D

    Dynamics Conservation of linear and angular momentum

    Attached file shows where my problem occurs. I understand how to get the angular momentum just before the collision. But what confuses me is is within the square. Why mvg(r) is only on the left hand side when I've had similar equations with it on both sides. Why is Ig used and why isn't Ib used...
  21. M

    2D Rigid Body Dynamics - Newtonian Equaitons of Motion

    Homework Statement In the diagram attached a bar weighs 500 kg and is a 2D plane rigid body with mass centre at G. At the instant shown, the bar is moving horizontally at but reducing speed, causing horizontal deceleration as shown by vector a=-7i m/s2. At the same time, the bar is being...
  22. H

    Rotational Dynamics: Net Torques

    Homework Statement Answer: C Note: Sorry admins for the picture, needed to include the diagram though. Homework Equations ∑\tau = I\alpha ∑F = ma a = \alphar The Attempt at a Solution The torques must be balanced (is this reasoning already wrong?), thus, F*R1 = F_T*R2 F_T =...
  23. H

    How to Calculate Tension in a Rotating Disk System?

    Homework Statement A 0.70-kg disk with a rotational inertia given by MR^2/2 is free to rotate on a fixed horizontal axis suspended from the ceiling. A string is wrapped around the disk and a 2.0-kg mass hangs from the free end. If the string does not slip, then as the mass falls and the...
  24. H

    Rotational Dynamics: Pulley and mass system

    Homework Statement A 8.0-cm radius disk with a rotational inertia of 0.12 kg*m^2 is free to rotate on a horizontal axis. A string is fastened to the surface of the disk and a 10-kg mass hangs from the other end. The mass is raised by a using a crank to apply a 9.0-N*m torque to the disk. The...
  25. O

    Magnetization Dynamics: Modeling the Ferrite Core of a Joule Thief

    I'm working on a project that involves a Joule thief. I need to model the magnetization process of the ferrite core of the toroid. With that I will be able to get an accurate picture of the flux change, which I can use to predict the induced emf based on the characteristics of the system...
  26. M

    Dynamics Module - Kinematics Problem

    Hi, I have an basic kinematics problem I can't seem to grasp -- hopefully someone can shed some light on it for me? The acceleration, a, of an object is equal to a=s, where s is the distance from the start position. Sketch a graph representing velocity against distance, s, for the...
  27. J

    Electromagnetism, dynamics and energy

    a 17KG cat is shot out of a hole in the side of a charged plate when the voltage is suddenly turned up to 5000V. The cat has a charge of 2.377^16c. He lands in a 3kg crate on wheels that has a µ=0.1 for o.50 meters. The crate is then put to stop by a spring 700 N/M. how much did the spring compress?
  28. Ascendant78

    Solve 1-D dynamics problem using integration and ?

    Solve 1-D dynamics problem using integration and ? Homework Statement A 75kg rocket is launched directly upward. The force on the rocket due to its engine decreases from 5000N to 0N as a quadratic function of time. The rocket reaches a speed of 200m/s during the time interval that its...
  29. T

    Rotational dynamics with constant CM velocity

    Hey PF! Homework Statement I've attached the problem to this post along with my free body diagram. Homework Equations Moment of inertia of a cylinder: 1/2MR^2The Attempt at a Solution Since the cylinder is moving at a constant velocity and is not slipping, ƩF = 0. For the torques around the...
  30. G

    Biological Fluid Dynamics - Approximate Navier Stokes Equations Solns

    Homework Statement Good evening. First post on this forum! The problem I wish to state would take too long to write by hand so I thought it best to do so via attachment. The question I am stuck on is part d and, in fact, part e also. Homework Equations All relevant equations are given...
  31. H

    Rotational dynamics question

    Homework Statement A large wheel has a radius of 7.1 m. A rope is wrapped around the edge of the wheel and a 7.6 kg box hangs from the rope. A smaller disk of radius 1.38 m is attached to the wheel. A rope is wrapped around the edge of the disk as shown. An axis of rotation passes through the...
  32. N

    How Do You Calculate Slingshot Maneuver Dynamics for a Space Probe?

    Really need help with this past exam question for revison: Homework Statement A probe performs slingshot maoeuvre around planet. Mass of planet is 9x10^22kg. Mass of probe is 4x10^2 kg and approaches planet from a great distance with relative speed 2x10^3 m/s and impact parameter 6x10^7...
  33. M

    Rotational Dynamics of a Cylinder Rotating Under an Applied Force

    Homework Statement A light rigid cylinder of radius 2a is able to rotate freely about its axis, which is horizontal. A particle of mass m is fixed to the cylinder at a distance a from the axis and is initially at rest at its lowest point. A light string is wound on the cylinder, and a steady...
  34. A

    Fluid dynamics and particulate diffusion question

    I have two cylindrical tubes connected at a 90 degree junction. One tube has a constant flow of a laminar fluid going through it and the fluid is saturated by a soluble particulate with a known concentration. The other tube has a much smaller radius, initially has no particles and is closed at...
  35. A

    Relation between liquid water pressure and it's molecular dynamics

    Hello everyone. I'm am looking for some literature (articles or books) containing information about how is the relation between the liquid water pressure (macroscopic thermodynamic quantity) and it's quantum molecular dynamics (collisions, vibrations, etc.). Like: The pressure increase...
  36. F

    Jun 26, 2013How to Find the Speed of a Block in an L-Shaped Track

    Homework Statement A small block of mass m is sliding around the inside of an L-shaped track of radius r. The bottom of the track is frictionless; the coefficient of kinetic friction and the wall of the track is μk. The block's speed is v0 at t0=0. Find an expression for the block's speed at...
  37. L

    Why Does Object A Reach the Bottom First in a Rigid Body Dynamics Experiment?

    Homework Statement Three objects of equal mass, A, B and C, are released from rest at the same instant from the same height on identical ramps. Objects A and B are both blocks, and they slide down their respective ramps without rotating. Object C rolls down the ramp without slipping. Its...
  38. A

    Rotational Dynamics: Analyzing Frictional Force Direction

    When I am browsing through my rotational dynamics chapter, I raise myself a question on the direction of frictional force under all kinds of possible circumstances: 1. Pure rolling For pure rolling, the frictional force will always be 0; 2. Non-pure rolling For this situation, I...
  39. R

    Archived Dynamics - 2 shafts rotating & connected with a clutch

    Dynamics -- 2 shafts rotating & connected with a clutch During the operation of a machine, two shafts rotate in opposite directions and are then connected by a clutch system. Shaft 1 has a rotational speed of 800 rev/min, a mass of 35 kg and a radius of gyration of 375 mm. Shaft 2 has a...
  40. N

    Dynamics: Planar Kinetics of a Rigid Body(Work and Energy)

    Homework Statement The operation of this garage door is assisted using two springs AB and side members BCD, which are pinned at C. Assuming the springs are unstretched when the door is in the horizontal (open) position and ABCD is vertical, determine each spring stiffness k so that when the...
  41. alane1994

    MHB Population Dynamics.... again

    Hey MHB, I have this rather large and convoluted project that consists of two problems. I have finished the first problem that consisted of 4 parts. I am working through the second part right now. It has a preamble that is kinda important. I will post that as well as the problems that I am...
  42. C

    Dynamics question regarding moment of inertia

    Hi, I have a question regarding a dynamics question that be found here:http://by.genie.uottawa.ca/~mess/files/MCG_2107/MCG2107_M2005_p2.pdf, It is the first problem on that link (labeled number 2.) I did ƩFx, ƩFy, ƩMG which allowed me to find angular acceleration, frictional force, and...
  43. B

    Is it difficult for engineers to switch to mathematical fluid dynamics research?

    Hi guys, I studied mechanical engineering and I am currently a graduate student (turbulence modeling). I am interested in the more formal/mathematical aspects of fluid dynamics, which are mainly worked in mathematical faculties and I would like to know if someone knows/have an idea about...
  44. misslogica

    Classical Dynamics Any help would be greatly appreciated

    Homework Statement A mass m1 is attached to a fixed spring on a horizontal surface and attached across a pulley (ignore the pulley mass) to another freely hanging m2. Write the Lagrangian in terms of a single parameter. Find the equation of motion and determine the frequency of oscillation...
  45. T

    Mechanical Engineering Dynamics Problem

    Homework Statement A plastic film moves over two drums. During a 4s interval the speed of the tape is increased uniformly from v0= 2ft/s to v1= 4ft/s. Knowing that the tape does not slip on the drums, determine (a) the angular acceleration of drum B, (b) the number of revolutions executed by...
  46. R

    Mechanical Principles - Dynamics.

    I hope I am posting in the right place. I am a 1st year University student. Although I am undertaking a BSc in Computer and Electronic System Engineering I have a Mechanical Principles module which I am finding a little bit of a struggle. Mechanical Principles - Dynamics: a) A diaphragm type...
  47. N

    Rotational Dynamics of two disks

    Homework Statement Two disks are spinning freely about axes that run through their respective centres (see figure below). The larger disk (R1 = 1.42 m) has a moment of inertia of 1070 kg · m2 and an angular speed of 4.2 rad/s. The smaller disk (R2 = 0.60 m) has a moment of inertia of...
  48. J

    How can I solve a dynamics problem involving a pulley, rod, and rotating masses?

    Homework Statement There is pulley which has a mass hanging from one side, and a rotating rod attached horizontally to the other (both by cables). The pulley has mass; Mp = 9.5kg and radius; Rp =0.2m. The block(A) has mass; Ma=10.9kg. The rod is L = 0.8m long and has mass=Ml7.9kg. The rod is...
  49. J

    Modeling Population Dynamics of Flies, Frogs, and Crocodiles

    Homework Statement Flies, frogs, and crocodiles coexist in an environment. To survive, frogs need to eat flies and crocodiles need to eat frogs. In the absence of frogs, the fly population will grow exponentially and the crocodile population will decay exponentially. In the absence of...
  50. D

    Dynamics- acceleration of beam on rollers

    1. Homework Statement 2200kg beam is sitting on two rollers spaced 2m apart. rollers weigh 1200kg and have radius of .35m. the block is pulled to the right with 4000N. there is no slippage. find the acceleration of the system (answer given is one of the rollers). 2. Homework Equations I...
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