What is Mechanics: Definition and 999 Discussions

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. H

    What is the Instant Centre of Rotation for a Rotating Bar?

    Homework Statement Homework Equations orthogonality condition: that means that the point of ICR is orthogonal to the velocity Vb and Va The Attempt at a Solution the solution that i found with the problem is: The ICR of the bar is at infinity. the motion of the bar is translational. I think...
  2. MARX

    Kleppner Mechanics: Disk and coil spring

    Homework Statement A solid disk of mass M and radius R is on a vertical shaft. The shaft is attached to a coil spring that exerts a linear restoring torque of magnitude Cθ, where θ is the angle measured from the static equilibrium position and C is a constant. Neglect the mass of the shaft and...
  3. Wrichik Basu

    Courses What is meant by "basic" quantum mechanics?

    I have been taking many online courses. In the prerequisites for many courses, it has been mentioned, "basic" quantum mechanics. It has become important to define where the boundary of basic ends and the advanced level starts, though I believe that is not well defined. I have been studying QM...
  4. P

    Question about Many Worlds branching in Quantum Mechanics

    Supposing the Many Worlds interpretation of QM is true... If a branching occurs during what we perceive is a wave function collapse, why would this be perceptible to us as probabilties? Wouldn't we just branch, leaving it just as imperceviable as the passage of time? That is, it just happens...
  5. U

    Rotational Mechanics question with spring

    Homework Statement A uniform cylinder of mass ##M## and radius ##R## is released from rest on a rough inclined surface of inclined surface of inclination ##\theta## with the horizontal as shown in the figure. As the cylinder rolls down the inclined surface, what is the maximum elongation in...
  6. Brilli

    Dependence of extention on length

    Homework Statement A light uniform spring is tied between the ceiling and the floor keeping the spring vertical as shown in the figure. A bead of finite mass is glued at a distance l from the upper end and then allowed to go slowly down. The bead shifts a distance y.How does the y depend on...
  7. U

    Applying W=F*s for variable force

    Homework Statement A car of mass 2000kg moves along a horizontal road against a constant resistance of manitude (P)N. The total work done by the engine in increasing its speed from 4ms^-1 to 5.5ms^-1 while it moves a distance of 60m is 30000J. Find P. Homework Equations ΔEk+WP=WE The Attempt...
  8. Boltzman Oscillation

    Other Can I apply what I learn in quantum mechanics to electrical engineering?

    Are there any projects I can build? What are the applications of QM in electrical engineering?
  9. Kushal Chakrabarti

    Constraint equations in mechanics

    1. The problem: Two blocks of mass m=5kg and M= 10kg are connected by a string passing over a pulley B. Another string connects pulley B to the floor and passes over pulley A. An upward force F is applied at the centre of pulley A. Both pulleys are massless. Find acceleration of the blocks if F...
  10. Don

    Popular book on Quantum mechanics

    I lost my book on Quantum mechanics! It was published in the late 80s or early 90s in England. Title: Quantum Mechanics. The book used algebra with more advanced math in the appendices. If you know the author , please reply. Thanks!
  11. SJay16

    QM and Statistical mechanics

    At my school, you have to take Quantum mechanics at the same time as Statistical mechanics (co-requisites) in either junior or Senior year as a physics major; why is this? What is the relationship between the 2?
  12. H

    Quantum Exploring Quantum Mechanics: ER=EPR, Black Holes, Firewalls & More

    ER=EPR, black hole complementary, firewalls, vacuum entanglement etc.. Where do I begin studying these new ideas? I have a solid understanding about Quantum Field Theory and the classical theory of gravity, but no knowledge of string theory. Are there some advice or book recommendations anyone...
  13. C

    I Particle Physics and Quantum Mechanics

    I’m having a hard time, as I begin learning QM, knowing what it applies to, if I can put it that way. Is QM the rules that describe how the particles of the Standard Model interact with each other? Or what is the best way to understand the relationship between what one studies when one studies...
  14. MARX

    Momentum Kleppner Classical Mechanics Freight Car and Hopper

    Homework Statement Freight car and hopper* An empty freight car of mass M starts from rest under an applied force F. At the same time, sand begins to run into the car at steady rate b from a hopper at rest along the track. Find the speed when a mass of sand m has been transferred.Homework...
  15. gmalcolm77

    Where Can I Find Free Online Courses on Quantum Mechanics?

    :rolleyes: I would like to find a free online course, not too hard. I have minors in math and physics, but have been away for awhile. Maybe something on youtube. If someone knows of a decent course that I could educate myself with I would appreciate any info on it. Thanks in advance...
  16. K

    I Interval in Quantum Mechanics?

    In Special/General Relativity invariance of a space-time interval is just so important. But in Quantum Mechanics, be it non-relativistic or QFT, there seems to be no such parallel. I have always noticed this. I have some ideas about the reason: 1 - it's not part of the theory to have a...
  17. Monsterboy

    In the context of statistical mechanics can anyone define temperature?

    I was told that defining temperature as the "average kinetic energy of the particles in a system" is not accurate enough.
  18. S

    Polymer Chain in Statistical Mechanics

    Homework Statement A polymer chain consist of a large number N>>1 segments of length d each. The temperature of the system is T. The segments can freely rotate relative to each other. A force f is applied at the ends of the chain. Find the mean distance ##\textbf{r}## between the ends...
  19. FourEyedRaven

    Quantum What's wrong with the Messiah "Quantum Mechanics" textbook?

    Hi. I bought Messiah's "Quantum Mechanics" because it was at an excelent price from Dover. But, even though it was considered a Bible of quantum mechanics until recently, people consider it outdated now. Is it no longer comprehensive? I intend to read on relativistic quantum mechanics and...
  20. WhiteWolf98

    Circular motion in the vertical plane

    Homework Statement A light rod ##AB## of length ##2a## has a particle ##P## of mass ##m## attached to ##B##. The rod is rotating in a vertical plane about a fixed smooth horizontal axis through ##A##. Given that the greatest tension in the rod is ##\frac {9mg}{8}##, find, to the nearest degree...
  21. Beanyboy

    It's official, Mechanics is hard

    So, I've been trying to study Mechanics in my spare time - about an hour or two every day - for over two years now. I'm up at 4:00 am most mornings studying before work. Despite being able to speak French, Italian and Irish fluently, holding a few Masters Degrees, and being a teacher myself, I...
  22. CDL

    Determining a Scattering Cross Section (Quantum Mechanics)

    Homework Statement Consider scattering of a particle of mass ##m## on the potential $$U(r) = \begin{cases} 0, & r \geq b\\ W, & r < b \\ \end{cases}$$ Where ##W## is some arbitrary chosen constant, and the radius ##b## is considered a small parameter. Find the cross section ##\sigma## in the...
  23. M

    Quantum mechanics: potential steps

    Homework Statement The Attempt at a Solution [/B] Hi All, I'm having trouble answering part (f) of the above question. I have managed parts (d) and (e) fine but am not sure how to proceed with part (f). I am pretty sure that the amplitude of the reflected wave in region 1 will be zero...
  24. U

    Studying Electrodynamics and Classical Mechanics?

    I am preparing for an exam which requires me to solve problems in electrodynamics and electrostatics problems along with classical mechanics and geometrical optics problems. The concern is that I do not have electrodynamics in my course in school so I have to study it completely on my own. I...
  25. B

    Solution approaches for large strain mechanics

    I’m studying large strain and deformation solid mechanics and I have a (seemingly) basic question on solution approaches. Is my interpretation below correct? The governing equation of momentum for solid mechanics can be solved using a total or updated Lagrangian approach. The updated...
  26. Z

    Derivation of the energy principle from Gregory Classical Mechanics textbook

    I'm working through Gregory's Classical Mechanics and came across his derivation of energy conservation for a system of N particles that is unconstrained. We get to assume all the external forces are conservative, so we can write them as the gradient of a potential energy. There's a step he...
  27. K

    Control Volume, Fluid Mechanics

    Homework Statement Water flows over a dam as depicted below. Across section 1 and 2 we have a hydrostatic pressure distribution. Calculate the force on the dam. The Attempt at a Solution My question is regarding control volume. The solution manual has given us this: The two hydrostatic...
  28. U

    Question Concerning The Coefficient of Friction: Block on a Rough Inclined Plane

    Homework Statement A block of mass 20kg is on rest on a rough plane inclined at 60 degrees to the horizontal. A force P is applied to the block to "maintain equilibrium". P is parallel to the line of greatest slope of the inclined plane. The maximum value of P is twice the minimum value of P...
  29. J

    Admissions One C in Classical Mechanics: Damnation?

    Hello, all. These are not the circumstances under which I would have preferred to have made my first post, but unfortunately, as the question suggests, this semester (second semester of freshman year), I earned a C in my calculus-based Intro to Classical Mechanics course. Not really for lack of...
  30. K

    Control volume, Fluid mechanics

    Homework Statement I have a situation as illustrated by the image above, where the red box illustrates the CV. The pressure on the left side of CV is P1, while the pressure on the right side of CV is P2. Here I´ve directed the pressure forces acting inwards on CV. The problem arises with Fk. I...
  31. K

    B Lack of Numerical Examples in Relativity & Quantum Mechanics: Exploring Reasons

    It's rare to encounter concrete, numerical examples of what is being taught about Relativity, Quantum Mechanics.. On the other hand there's plenty of numerical examples in the undergraduate general physics textbooks, for instance problems of mechanics. As for General Relativity I did find only...
  32. Riotto

    I Perturbative versus nonperturbative quantum mechanics

    What is the nonperturbative approach to quantum mechanics as opposed to perturbative one? When does the latter method fail and one has to apply nonperturbative approach? Please keep your discussion confined within non-relativistic quantum mechanics.
  33. L

    Relative velocity of exhaust in Ideal Rocket Equation

    In this derivation of the Ideal Rocket Equation (https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation#Most_popular_derivation), they use the fact that ##V_e = V - v_e##, or that the velocity of the exhaust in the observer frame ##V_e## is the velocity of the rocket ##V## minus the speed of...
  34. R

    Acceleration of a cart immediately after the system is released

    Homework Statement : A block B of mass m is suspended from a cord of length l attached to cart A of mass M as shown in the figure. The horizontal surface on which the cart moves is smooth. Initially the cart and the block are at rest in the position shown. Now the block is released. Take M=2kg...
  35. A. Neumaier

    I Relativistic hidden variable quantum mechanics?

    I just came across the following paper: Gisin, N. (2011). Impossibility of covariant deterministic nonlocal hidden-variable extensions of quantum theory. Physical Review A, 83(2), 020102. proving that, under sensible hypotheses, nonlocal hidden variable theories for relativistic quantum...
  36. R

    Where is the hinge point? & what is the moment of inertia of a square?

    Homework Statement :[/B] A uniform wire of linear mass density λ having three sides each of length 2a is kept on a smooth horizontal surface. An impulse J is applied at one end as shown in the figure. P is the midpoint of AB. Now answer the following questions. 1) The angular velocity of system...
  37. WhiteWolf98

    Vectors/ Calculus with i and j components

    Homework Statement I don't understand how to form an equation using the knowledge that, 'When ##t=4##, ##P## is moving parallel to the vector ##\mathbf {j}##'. I've seen the solution, and not a single part of it makes sense. I haven't attempted any question like this before, so I have no idea...
  38. B

    Stress Used in Lagrangian Equation for Solid Mechanics

    Bathe (reference below) outlines the updated Lagrangian (UL) and total Lagrangian (TL) approaches using the second Piola Kirchhoff (PK2) stress. Others (i.e., Ji, et al. and Abaqus) define the UL and TL formulations in terms of the Kirchhoff or the Cauchy stress in rate form. This form requires...
  39. ubergewehr273

    Problem about an impulse and a spring

    Homework Statement The attached image. Homework Equations Momentum conservation Conservation of mechanical energy The Attempt at a Solution I tried conserving momentum, ##P=mv_{1} + Mv_{2}## and then conserving M.E., P^2/(2m)=1/2##mv_1{1}^2## + 1/2##Mv_{2}^2## After that I can't seem to...
  40. D

    Force-Deformation Equations Application

    Just found this forum--hope there isn't a max post limit haha. I have been a bit stumped on this, but when doing problems about deflection and axial loadings, I am confused when to use which equation. I think I know that axial member need to be 2 force members, loaded only at the ends, and...
  41. binbagsss

    Statistical Mechanics: Can one assume an idealized gas is non-relativistic

    In general when one talks about an idealized gas, should/could one assume it is non-relativistic? (s.t E=p^2/2m will hold) many thanks
  42. Brilli

    Efficient Path Tracing: Solving for Time and Motion with Inclined Planes

    Homework Statement A small disk A is placed on an inclined plane forming an angle (alpha) with horizontal and is imparted an initial velocity v. Given coefficient of friction =k and ant initial moment angle of velocity =90 degrees. Find out how long it takes to come ro rest and give the...
  43. D

    I Static analysis of bicycle frame - Need some clarification

    Hey, I am interesting in analyzing a bicycle's frame statically from a vertical fall of x metres, this after using the energy principle i get that the force F = mv^2/r, where v = sqrt(2*g*h), r is the deformation of the bicycle at its contact point and m is total mass from the cycle and cyclist...
  44. J

    Statistical mechanics and the weather

    Hi all. Where can I find some good introductory sources teaching the use of statistical mechanics to study things like tornado formation or climate in general? I took P. Chem., a while ago now but I'm reviewing the material independently. We used one of Moore's texts, 80's - ish, and in it he...
  45. T

    Classical A General Physics refresher book?

    Hi everyone, I just created this account because it was actually the first time I wanted to ask a question myself, but this forum has helped me a lot in the past with my Physics and Maths related courses. So thank you for that. Going back to the topic...Now that I've completed some of the...
  46. BookWei

    Velocity is a vector in Newtonian mechanics

    I studied the vector analysis in Arfken and Weber's textbook : Mathematical Methods for Physicists 5th edition. In this book they give the definition of vectors in N dimensions as the following: The set of ##N## quantities ##V_{j}## is said to be the components of an N-dimensional vector ##V##...
  47. W

    Position mean in momentum-space (QM)

    Homework Statement Find ##\langle x \rangle## in the momentum representation I am having trouble understanding some of the steps needed to get to the expression, assistance is greatly appreciated! Homework Equations 3. The Attempt at a Solution [/B] $$\langle x \rangle = \langle \psi | x |...
  48. TaylorLL

    Rocket subject to linear resistive force -- two methods

    Homework Statement Consider a rocket subject to a linear resistive force, $$f = -bv$$, but no other external forces. Use Equation (3.29) in Problem 3.11 to show that if the rocket starts from rest and ejects mass at a constant rate $$k = -\dot{m}$$, then its speed is given by: $$v =...
  49. Maria

    Simple closed force system -- Mechanics

    Homework Statement There is a system of 4 points located along a circle of radius R. Points are connected by undeformable ropes (pink on the picture). There is a force applied to each point. Scheme: https://we.tl/MsCEViCQdB I need to find resulting force in the system. The Attempt at a...
  50. Q

    Independence of Position and Velocity in Lagrangian Mechanics

    In Lagrangian mechanics, both q(t) and dq/dt are treated as independent parameters. Similarly, in Hamiltonian mechanics q and p are treated as independent. How is this justified, considering you can derive the generalized velocity from the q(t) by just taking a time derivative. Does it have...
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