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. L

    Water dynamics, well piping help

    I would like to pipe a water well ( using gravity alone) with a 250m run and an overall fall of 3m. A large barrier (a hill) is middle ways . The last 100m down the hill has most ,if not all the fall. The question is if I pipe this last 100m with a larger diameter (from 3/4" going to 1") would...
  2. M

    Ability to customise in fluid dynamics experiments

    Is it usual to customise experiments in fluid dynamics and to what extent? I understand that lasers and imaging tools will be fairly untouchable by a fluid dynamicist, although does an experimental role require any 'tampering/customising of general system equipment i.e. rewiring/handy work...
  3. F

    Lagrangian dynamics problem.

    A point of mass m, affected by gravity, is obliged to be in a vertical plan on a parabola with equation z = a.r^2 a is a constant and r is the distance between the point of mass m and the OZ vertical axis. Write the Lagrange equations in the cases that the plan of the parabola is : a) is...
  4. C

    How Much Clamping Force to Prevent a Ball from Slipping in Robotic Grippers?

    Homework Statement The static friction coefficient between the grippers and the ball is 0.5, and the grippers hold the ball such that they touch the middle of the ball on opposite sides. Find the clamping force required to keep the ball from slipping out, if the ball weighs 10 lb...
  5. D

    Dynamics - Motion in a Plane, Problem

    Homework Statement A 5000kg rocket is launched at 44.7º with a thrust of 140,700N. a. Find an equation y(x) that describes the rocket's trajectory. b. Shape of trajectory? c. At what elevation does the rocket reach the speed of sound, 330m/s? Homework Equations F=ma The distance...
  6. M

    Solving a pulley system (Dynamics)

    Solving a problem about a pulley system (dynamics) A 100 kg crate is supported by a rope which passes over a 25 kg pulley. A 2nd rope connects the pulley to the ceiling. The system is stationary. ƩFx=0 ƩFy=0 I am having problems setting up the free body diagram to start the problem!
  7. T

    Path following control robot kinematics and dynamics

    Hello, I have a general question regarding what is the best controller (PI, PD, etc.) to control the position of a mobile robot in order to follow a known path. The mobile robot at hand is a mechanism (a 4 bar linkage with its two base gliding on two parallel but not straight rails) and I...
  8. A

    Why do we take convective derivative in fluid dynamics

    I am studying plasma physics. While treating the plasma as a fluid, we replace the generla time derivative of velocity of any particle by the convective derivative. I would like to know the reason and also what is the frame of reference when we work with fluid dynamics.
  9. M

    Dynamics: impulse and momentum

    Homework Statement a 200-g projectile is fired with a velocity of 900m/s towards the center of the 15-kg wooden block, which rests on a rough surface. If the projectile penetrates and emerges from the block with a velocity of 300m/s, determine the velocity of the block just after the...
  10. M

    Dynamics question about boy pulling himself up via pulley

    Homework Statement A 45 kg boy stands on 30 kg platform suspended by a rope passing over a stationary pulley that is free to rotate. The other end of the rope is held by the boy. The masses of the rope and pulley are negligible. Ignore the friction in the pulley. a) If the rope and the...
  11. A

    IVP involving Eigenvalues and Population Dynamics

    Homework Statement Consider the interaction of two species of animals in a habitat. We are told that the change of the populations and can be modeled by the equations \frac{dx}{dt}= 0.1x-0.8y \frac{dy}{dt}=-0.2x+0.7y Find the solution to the above equations with initial values x(0)=9 and...
  12. S

    A Room with a Window and a Fan; Air Pressure Dynamics

    If room A is connected to the outside with a window and room A has a fan on; Would the air would try to move out from room A to the outside because there is a higher pressure inside the room? in concept
  13. Z

    I need a lot of help with Kinematics and Dynamics so forces and motion

    I need a lot of help with Kinematics and Dynamics so forces and motion would be what you can call that. I have a teacher that does not teach, I have had her for two years in a row now so if I had some knowledge from grade 11, It would still help me but I learned close to nothing in Grade 11 and...
  14. 7

    What are the forces at play in Sally's car rescue scenario?

    Hey, I'm having problems with this questions Sally’s car is stuck in a snow bank, but she is very knowledgeable about physics. She ties a rope from her car to a tree 25.0 m away and then pulls sideways on the rope at the midpoint. If Sydney applies a force of 425 N and draws the rope over a...
  15. J

    What are the best online help sources for dynamics?

    I used to watch youtube videos for general physics and statics but I can't seem to find good help sources for dynamics. Does anybody know of a good youtube channel that has helpful videos for the dynamics course or any other websites that help make more sense of the class? If not, can...
  16. 3

    Solving a Vertical Winch System

    Hey! I'm having some problems with this question: An electric winch is used to raise a 40-kg package and a 10-kg package vertically up the side of a building as pictured in the diagram. The magnitude of the frictional force acting between the wall and the 40-kg package is 60N. The angle the...
  17. M

    Exploring the Relationship Between Work, Energy, and Forces in Dynamics

    One question about this excercise. Why "W" isn't included in the sum of forces? Is doing work because is in the same direction of the movement, so I would assume that both the force of spring and weight would be in in my sum of forces. But this is not the case here, why is that?
  18. M

    Is fluid dynamics a true physics subject?

    Are fundamental discoveries made in fluid dynamics currently, or is it just particular solutions based upon known fundamentals? From reviewing journal literature, it appears that either application based problems have been studied (engineering), or fluids under certain conditions that form a...
  19. M

    Dynamics Polar Coordinates question

    Hi everyone. I am a little desperated cause my exam is on monday and still much stuff to do. I don't get when I am supposed to use/consider radial and tranversal forces. Most excercises say "it rotates on the horizontal or vertical" I guess this is the info that tells me if there is...
  20. F

    Simulation for galaxy dynamics

    Hello, I'm trying to simulate disc galaxy dynamics with a nbody code. The main problem is to get good initial values (positions and velocities of each star) in order to reproduce the experimental dynamics. For the positions, I began by generating a gaussian distribution of stars on 0x...
  21. A

    Fluid dynamics: Knowledge continuity equation

    Homework Statement Please click on the link for the question. http://i1154.photobucket.com/albums/p526/cathy446/physicsquestion_zps49e16ab1.jpg Assume that air spreads out after coming out from the tube at 2. The speed over tube 1 is almost zero. Homework Equations Knowledge problem on...
  22. S

    Beyond the norm Dynamics question

    Hey Guys, I have tough dynamics question. I wasn't sure if this is the best place to post it, so if it isn't please let me know. I thought it might be because I couldn't find anything about it anywhere. So here goes. If one had 10 inch long hose, 1" in diameter, filled with some incompressible...
  23. H

    Solve 1D Dynamics Problem: Can Car Stop Before Intersection?

    1D Dynamics Problem! Homework Statement A car of mass 1100kg is traveling at a constant velocity of 60 km/hr, east. The coefficient of friction between the tires and the road is 0.45. The driver of the car sees the traffic light in front turning red and steps on the brake, only to find that...
  24. E

    Motor in a pulley system with weight help (Sort of a dynamics problem)

    Homework Statement At the instant shown, point P on the cable has a velocity 12 m/s, which is increasing at the rate of 6m/s^2. Determine the power input of motor M at this instant if it operates with an efficiency of 0.8. The mass of the block A is 50kg. I've attached a picture of the...
  25. E

    Engineering Motor and Pulley System with weight help (Kind of a Dynamics Problem)

    Homework Statement At the instant shown, point P on the cable has a velocity 12 m/s, which is increasing at the rate of 6m/s^2. Determine the power input of motor M at this instant if it operates with an efficiency of 0.8. The mass of the block A is 50kg. I've attached a picture of the...
  26. Nono713

    Fluid dynamics, friction and pressure

    Hello, this is not homework, I am trying to derive some physics results using intuition, I am currently looking at some fluid dynamics problems. Consider a water droplet on a frictionless horizontal plane, subject to gravity. The cross-section of the droplet would look something like this...
  27. M

    Solve Dynamics Problem: Find Time & Height of Cliff

    Homework Statement From the edge of a cliff, two stones are thrown at the same time, one vertically upwards and the other vertically downwards with the same velocity of 20 m/s. The second stone reaches the ground in 5 s. How long will the first stone be in air? Also find the height of the...
  28. E

    Why Force Due to Friction Not in Equation of Motion?

    Why is ft (the force due to the friction between the cylinder and the ramp) not included in the equation of motion?
  29. T

    Dynamics of Machine Course Help

    Hi All, I was wondering if anyone could post some videos or some websites where I can read about Dynamics required for Mechanical Engineering i.e. related to vectors , how to add vectors , how to find the resultant. I searched YouTube but I am not really getting any good responses. I am a...
  30. N

    Second Law of Dynamics: Important Consequences

    Hi everyone! I saw in an old exam of physics : "Write and comment the second law of dynamics." And i was thinking, I know a lot about it and if i had to answer it i would have made some examples, but when he asks me to comment it ? What should i have to say ? In sense, what do you think are...
  31. A

    Urgent Dynamics Problem Help Needed: 12-101 Hibbler 13th ed.

    The Problem. 12-101 Hibbler dynamics 13th edition. It is observed that the skier leaves the ramp A at an angle θA=15 degrees with the horizontal. if he strikes the ground at B, deterime his initial speed VA and the speed at which he strikes the ground (at B)...
  32. mfig

    Check my solution to this dynamics problem.

    Hello, I found this problem while preparing for the qualifying exams and thought I would tackle it. I have no idea if it is correct, but I would like someone to tell me if there is an easier way to solve this than I used. Perhaps some Lagrangian or Hamiltonian approach? Thanks. The...
  33. A

    Solving Dynamics Problems with Burden's Self-Study: Momentum & Kinetic Energy

    Good morning all. I wondered if anyone could assist me with the following dynamics problem. The question is copied from Burdens Dynamics and Mechanical Sciece Self Study. Question) Three balls of mass 2kg each, have a coefficient of restitution of k = 0.85. Ball A is released at a height of...
  34. D

    Simple Dynamics question (just help to check the answer)

    Okay I have done it, but have a feeling that there's something wrong. I don't have the solution/answer so it will be great if someone can help me check. more of part 2 (which leads to part 3) Homework Statement a body of mass 6.0kg and density 450kg/m^3 is dropped from rest at a height of...
  35. K

    Rotational Dynamics about an axis parellel to the axis at the center of mass

    Homework Statement A uniform sign is nailed into a wall at its top two corners. The nail on the upper-right corner breaks, and the sign begins to rotate about the remaining nail in the upper-left corner. The mass of the sign is 69 kg, L (length) = 1.6 m, H (height) = 2.2 m, and the moment of...
  36. Q

    3D Rigid body dynamics - Rod over rotating disk

    Homework Statement A thin uniform rod is attached to an axis through its midpoint. The axis is standing on a disk rotating with constant angular speed \Omega about its symmetry axis. The rod's midpoint is located directly above the rotational axis of the disk. Let \theta denote the rod's...
  37. L

    Model Dynamics of Unit Mass Sliding Down y=f(x) Under Gravity

    For a unit mass sliding down the stationary curve y = f(x) at the point (x, y), we can consider our mass to be sliding down a stationary inclined plane which is tangential to the curve at the point (x, y). The slope of this inclined plane is thus \frac{dy}{dx}(x). For the remainder of this...
  38. H

    [help please] Difficult Dynamics Challenge

    Hello all, Semester has just started and i am dong a 4th year dynamics unit, so i am reviewing the previous years unit which was a pre-requisite for the unit i am currently doing. I have come across a rather difficult dynamics problem that was given as a challenge question at the beginning of...
  39. H

    Statics and Dynamics problem

    Homework Statement You are working for the Peace Corps in a developing country. Your job is to design a simple, but accurate scale for weighing bulk materials such as food and construction materials. A possible idea consists of a loading platform, D, that is supported by cable AB, where end...
  40. A

    Unable to solve type of question (dynamics): finding coefficient of friction

    So I've been busting my head for the past 2 days trying to figure out what I was doing wrong and I just can't. I have a whole bunch of these types of questions and can't solve any of them. My own equations and reasoning make sense to "me" but don't lead me to the right answer. I am positive I'm...
  41. A

    Dynamics Question: Finding Fa using mass and acceleration

    Hello again forum :smile: I am still studying for that unit test and am still having problems with dynamics... I've attached the problem with the calculations/solutions. Basically, I don't understand why I'm getting the wrong answer. Probably b/c idk what the heck I'm doing :eek: Homework...
  42. A

    Dynamics Question: Finding mass using Vi, Vf, D and acceleration

    Hi everyone, I'm new to forum and am a 3rd year university student who has never taken physics until now.. I'm currently studying for a dynamics unit test and came upon this question... Homework Statement A car whose brakes are locked skids to a stop in 70m from an initial velocity of...
  43. N

    [fluid dynamics] are they trying to use the ideal gas law for LIQUIDS?

    In my course they're using the equality U = \frac{p}{\alpha \rho} with alpha some constant (U = internal energy per mass, p = pressure, rho = density). They explicitly derive it for an ideal gas yet later apply it to a liquid (in the context of deriving the Navier-Stokes energy equation). Seems...
  44. X

    Simple pendulum dynamics; equations of motion, work and energy

    Homework Statement See attachment "problem" Homework Equations Euler's laws of motion (moment equations), work and energy equations The Attempt at a Solution See attachment "work" I did the work for (1) and (2). I end up with two equations: the first is the tension T, the second...
  45. N

    [fluid dynamics] why are there no shear forces in a fluid at rest?

    It is said that the stress tensor \mathbf T for a fluid at rest is diagonal. Why is this? The fact that the fluid is at rest means there is no net force, i.e. the body and surface forces cancel each other: 0 = \mathbf F + \nabla \cdot \mathbf T, but from this condition is does not follow...
  46. N

    Applying Reynold's Theorem to Infinitesimal Element: Fluid Dynamics

    So Reynold's transport theorem states that \frac{\mathrm d}{\mathrm d t} \int_{V(t)} f \; \mathrm d V = \int_{V(t)} \partial_t f \; \mathrm d V + \int_{V(t)} \nabla \cdot \left( f \mathbf v \right) \; \mathrm d V. Now I would expect (on basis of conceptual reasoning) that if I were to apply...
  47. J

    Ventaliation Fluid Dynamics

    Hi I'm creating a hamster cage for better ventilation(circulation) without too much flow.(draft) How would I work out mathematically the air flow going into a plastic box. The flow rate etc.. The plastic box will be inside a normal home. Things I want to know and improve The overall...
  48. S

    Double slit confusion from observed particle dynamics.

    Hey Guys, I continue to get mixed messages about the nature of electron behaviour during the double slit experiment. I have heard the term observation used to describe an interaction with the electron (Obviously necessitating a change in it's behaviour to facilitate the ballistic outcome)...
  49. S

    Dynamics of a particle moving in a straight line question

    A car of mass 900 kg is towing a trailer of mass 300 kg along a straight horizontal road. The car and the trailer are connected by a light inextensible tow-bar and when the speed of the car is 20m s−1the brakes are applied. This produces a braking force of 2400 N. Find a the deceleration of...
  50. Q

    Fluid dynamics - Where to post questions?

    Fluid dynamics -- Where to post questions? Is this the place to post to discuss fluid dynamics?
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