Theoretical mechanics Definition and 22 Threads

Mechanics (Greek: μηχανική) is the area of physics concerned with the motions of physical objects, more specifically the relationships among force, matter, and motion. Forces applied to objects result in displacements, or changes of an object's position relative to its environment.
This branch of physics has its origins in Ancient Greece with the writings of Aristotle and Archimedes (see History of classical mechanics and Timeline of classical mechanics). During the early modern period, scientists such as Galileo, Kepler, and Newton laid the foundation for what is now known as classical mechanics.
It is a branch of classical physics that deals with particles that are either at rest or are moving with velocities significantly less than the speed of light.
It can also be defined as a branch of science which deals with the motion of and forces on bodies not in the quantum realm. The field is today less widely understood in terms of quantum theory.

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  1. M

    Theoretically, could shrinking down to Planck scale enable time travel?

    I remember one of the Ant-Man movies had time travel enabled by shrinking down to an incredibly small size. This seemed silly to me at first but then I realized that a second is much closer to the age of the universe than a Planck time is to a second. This is mind-boggling and the human brain...
  2. ardaoymakas

    Hamiltonian Function thru new Variables Q,P -- Show that Q is cyclic

    I took the derviative of the Hamiltonian function with respect to Q and assumed that it was equal to 0 in order to find the Konstant A. I did find the Konstant A as -1/2m^2g but I still cant write the Hamiltonian equation without having the Q as a variable. Can someone please help? Translation...
  3. 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...
  4. M

    Calculating Time to Reach Highest Point in Theoretical Mechanics Problem

    A rough explanation of my attempts: I set the coordinate axis in a way that x is the horizontal base and y is perpendicular. But I guess it is a 3d problem, so I struggle finding the right position of the coordinate system. Then, my next step was applying 2nd NL for every axis. So far I have...
  5. J

    A Liouville's theorem and time evolution of ensemble average

    With the Liouville's theorem $$\frac{{d\rho }}{{dt}} = \frac{{\partial \rho }}{{\partial t}} + \sum\limits_{a = 1}^{3N} {(\frac{{\partial \rho }}{{\partial {p_a}}}\frac{{d{p_a}}}{{dt}} + \frac{{\partial \rho }}{{\partial {q_a}}}\frac{{d{q_a}}}{{dt}})} = 0$$ when we calculate the time evolution...
  6. aligator11

    Particle Dynamics Problem (kinematics)

    Summary: Mechanics problem related with Calculus (differential equations) Hi everyone, I would like some help in that task, if anyone would be willing to help :) Namely I have a problem from particle dynamics. "D:" means given info... so, D: m,g,h,b, miu. We're looking for v0 and S as given...
  7. S

    Is there place for higher order derivatives in mechanics?

    The building of theoretical mechanics can be constructed using only the first and the second derivatives (those of coordinates in case of kinematics: velocity and acceleration and those of energy in case of dynamics: force and gradient thereof). It is obviously unavoidable if one wants to deal...
  8. O

    Lagrangian of system with circle and cube

    Hello. I have some problems with making Lagrangian. I need your advice. 1. Homework Statement I have this situation: Consider the circular path is intangible and without friction. I have to find Lagrangian for coordinates x and θ. Homework Equations [/B] L = U - V The Attempt at a...
  9. S

    Small oscillations and a time dependent electric field

    Homework Statement [/B] Here's the problem from the homework. I've called the initial positions in order as 0, l, and 2l. Homework Equations The most important equation here would have to be |V - w2*M| = 0, where V is the matrix detailing the potential of the system and M as the "masses" of...
  10. K

    Dynamics of a point mass in circular motion

    Homework Statement Dear All, I'm having a hard time solving the following problem: A point of mass is moving on a circular plane (Oxy), where the circle's formula is: The force acting on mass "m" is defined as: We're looking for velocity of point "m" in position (1,1) =V1, and in position...
  11. smodak

    Classical Found a great resource on Theoretical Mechanics (free)

    Classical mechanics: a minimal standard course by Sergei Winitzki. It is not probably going to help you if you already did not know the subject but is a great refresher nonetheless. He also includes a differential equations refresher that I found invaluable. Looks like he has a ton of other...
  12. V

    I GR: How Much Mechanics is Involved?

    I'm currently taking a course in Theoretical Mechanics, which is a prerequisite to General Relativity, which I'm very much looking forward to taking. However, I'm not that good in mechanics, and Real Analysis seems to be more straightforward than even the first course in Mechanics. I'm quite...
  13. J

    Gear Ratios and Constant Power/Torque: find max velocity?

    I'm trying to determine how exactly gear ratio limits velocity. I know that a high torque configuration is generally regarded as low speed, but my calculations do not seem to support that. Basically, I've written a small problem where we have an input gear with constant torque and an output...
  14. M

    Analyzing Relativistic Effects on Low-Flying Satellites

    Homework Statement [/B] A low flying Earth satellite travels at about 8000m/s. For the satellite, the relativistic factor $$\gamma = \frac{1}{\sqrt{1-\beta^2}}$$ where $$\beta = \frac{v}{c}$$ is close to 1 because v<<c. Estimate by how much gamma actually deviates from 1 by expanding gamma in...
  15. M

    How can I solve for v(t) when given F=Fo and v(t=0)=0?

    Homework Statement Homework EquationsThe Attempt at a Solution See LaTeX[/B] given that $$v^2 = v_o^2 + \frac{2}{m}\int\limits_{x_o}^x F(x) \ dx\ $$ find the speed v(t) and the position x(t) given that $$F = F_o$$ and $$v(t=0)=0$$. I tried plugging in $$F=F_o$$ for $$F(x)$$ in the above...
  16. M

    Calculating Force and Displacement for a Particle in Advanced Mechanics

    I'm new to this site, so please bear with me. 1. Homework Statement A particle of mass m has speed v(x) = α/√x. Calculate the force F(x) responsible. Then, calculate the displacement x(t) of the particle. Homework Equations [/B] The equations that I believe we are supposed to use are f=ma...
  17. S

    How to study Theoretical Mechanics?

    I know Single variable Calculus and I have a basic understanding of multivariable calculus. I also happen to know basic linear algebra. What are the mathematical pre-requisites needed in order to self-study theoretical mechanics? I'm planning to take this course...
  18. Alexandre

    How to derive lagrangian for any classical system?

    Suppose I come up with a system that has certain number of particles with certain masses and are interconnected between each other in a certain way and are acted by forces which are also part of the system. What's the general rule for finding potential and kinetic energies as functions of...
  19. PsychonautQQ

    Theoretical Mechanics: velocity dependent force

    Homework Statement A projectile is launched horizontally. A retarding force acts on the projectile of the form F = -Ae^(cv). Find it's speed as function of time. Homework Equations F = ma The Attempt at a Solution m(dv/dt) = -Ae^(cv) e^(-cv) dv = (-A/m) dt I integrated the...
  20. Greg Bernhardt

    Particle Theoretical Mechanics of Particles and Continua by Fetter

    Author: Alexander L. Fetter Title: Theoretical Mechanics of Particles and Continua Amazon Link: https://www.amazon.com/dp/0486432610/?tag=pfamazon01-20
  21. J

    Theoretical mechanics question

    Here's a simple question. Anyone who knows the answer can save me from some effort by telling the answer. For arbitrary canonical transform (q,p)\mapsto (Q,P) in the Hamilton's formulation, does there always exist a corresponding transformation q\mapsto Q in the Lagrange's formulation? By...
  22. A

    How Do You Solve Particle Motion Equations in an Electromagnetic Field?

    So I'm stuck on the second part of this problem and really don't know hwere to go from here... let me type it up and show where I got stuck at. 3. The motion of particle of chage q in an electromagnetic field is governed by the Lorentz force (for low velocities v<<c): F=qE + qvxB. With both...
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