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. thaiqi

    Quantum Which books are best for learning Bohm's mechanics?

    Hello, everyone. Which books best for learning Bohm's mechanics?
  2. thaiqi

    Deriving Statistical Behavior of Particles via Classical Mechanics

    Hello, using computation simulation, can the statistical behavior of many particles be derived through deterministic classical mechanics?
  3. TechieDork

    Courses I think I won't get an A in Quantum Mechanics I

    This is by far the hardest undergraduate class I have ever take. The majority of class got less than 40% on the midterm. Unfortunately, I was sick during the exam hours too ,so it's hard for me to concentrate and think clearly Thank god,the professor uses the norm-referenced grading and My...
  4. JD_PM

    Classical Book on discrete mechanics (particularly interested in Lagrangian)

    Hi.I am looking for a book to learn about discrete mechanics (i.e. working in a 3D lattice instead of ##n## generalized coordinates). I am particularly interested in how to derive the discrete E-L equations by extremizing the action. I have checked Gregory and Goldstein but they do not deal...
  5. E

    Griffiths Quantum Mechanics 2nd edition Chapter 8 equation is confusing

    In Griffiths Quantum Mechanics 2nd edition, in Chapter 8 he calculates the following integral on page 323 and he gets I disagree with this result, I think the integral should be since Maybe somebody can explain why I am wrong? Also, from equation 8.24 to 8.25, he makes the assumption that...
  6. Boolean

    Lug FBD and simple mechanicals

    Pretty simple FBD of a lug in a pull test that I solved using FEA software, but I’m having trouble checking with a hand calc. Back end is fully supported in a test fixture Feel free to make up numbers where not given
  7. S

    Classical mechanics -- Equations for simulating the motion of a body

    Hello forum, i want to make a samulation of a body. The body will be moved horisontal on y,x axis. I want on my simulation the body to change direction many times(for example i want to go for 10sec right and then left end right...). My question is does i need more than one differential equation...
  8. M

    Physics C: Mechanics - Negative Energy and Potential Energy Curves

    I'm currently taking a course where we are working to teach older physics concepts and combine them with calculus. I was assigned to work on teaching a unit about energy; for the most part, it stays relatively consistent and can be solved algebraically. Another topic in this unit is Potential...
  9. chocopanda

    Quantum Mechanics: creation and annihilation operators

    Hello everyone, I'm new here and I'm struggling with the mathematical formalities in quantum mechanics. $$\langle n+1|b^\dagger bb^\dagger + \frac 12 |n \rangle = \langle n+1|b^\dagger bb^\dagger |n \rangle + \langle n+1| \frac 12 |n \rangle $$ $$ = \langle n+1|b^\dagger b \sqrt{n+1} |n+1...
  10. T

    Mechanics; grade 12 Projectile motion

    Summary:: Scooby-Doo wants a Scooby Snack. According to a website I looked up last night, Scooby can run at a speed of 36 km/h. He runs up a ramp (as shown, 2.0 meters high, 4.0 meters long) at that speed and off the edge. Three meters from the end of the ramp, Shaggy has a Scooby-Snack...
  11. Jamister

    I Understanding Matrix Mechanics in Quantum Mechanics

    In a course of QM they mention Matrix mechanics. But what is it exactly? Is it just Heisenberg picture?
  12. Jamister

    A An experiment that claims to doom Bohmian Mechanics

    I read in the article in Quanta magazine about an experiment with oil droplets that dooms Bohmian Mechanics, but I didn't understand why. Does anyone knows this experiment and why it dooms Bohmian Mechanics? The article is in the link...
  13. person123

    Inertial Force in Fluid Mechanics

    According to one explanation, the left hand acceleration terms of Navier Stokes equations are the called the inertial terms. If you were to balance forces on the fluid particle, they would have to be equal and opposite to the forces on the right hand side (pressure gradient, viscous, and body)...
  14. Vanilla Gorilla

    I Would Black Holes Be Coherent Under Quantum Mechanics?

    I just want to know if Black Holes would be quantumly coherent.
  15. Another

    Problem about Lagrangian mechanics

    In Solution https://www.slader.com/textbook/9780201657029-classical-mechanics-3rd-edition/67/derivations-and-exercises/20/ In the question say the wedge can move without friction on a smooth surface. Why does the potential energy of the wedge appear in Lagrangian? (You can see the Larangian...
  16. Jamister

    Programs Searching for universities to do my PhD on foundations of quantum mechanics

    I want to do my Phd on foundations of quantum mechanics, but I don't find researchers in the U.S.A that work on that. Is there a good way to search other than to go to each university and go over the PI's? Thanks
  17. Mayan Fung

    I Energy operator in Quantum Mechanics

    I learned that the energy operator is ##\hat{E} = i\hbar \frac{\partial}{\partial t} ## and the Hamiltonian is ##\hat{H} = \frac{-\hbar^2}{2m}\nabla^2+V(r,t)## If the Hamiltonian represents the total energy of the system. I expect the two should be the same. Did I misunderstand the concept of...
  18. 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...
  19. T

    Lagrangian mechanics, system of a spring and a pendulum

    Hello! I have some problem getting the correct answer for (b). My FBD: For part (a) my lagrangian is $$L=T-V\iff L=\frac{1}{2}m(b\dot{\theta})^2+mg(b-b\cos\theta)-\frac{1}{2}k\boldsymbol{x}^2,\ where\ \boldsymbol{x}=\sqrt{(1.25b-b)^2+(b\sin\theta)^2}-(1.25b-0.25b)$$ Hence my equation of...
  20. S

    Mechanics: Find the minimum initial velocity and angle of this projectile

    Attempt at solution in attachment.
  21. AN630078

    Mechanics: Motion of Two Connected Vehicles

    i. Using Newton's 2nd Law, F = m a consider the motion of the entire system, so the car, caravan and towbar an be thought of as a single object. The tension can ignored as it is an internal force. Braking fore + resistive forces = mass * acceleration Braking force + 200N +150 N=(1000+1500)*(0.5)...
  22. AN630078

    Mechanics: Explosion of an Object Vector Diagram

    Well, I understand that according to the conservation of momentum the total momentum of a system is conserved for objects in an isolated system, that is the sum of total momenta before the collison is equal to the sum of momenta after the collision. In this case, the momentum of the object...
  23. AN630078

    Mechanics: Elevator Accelerating Downward

    The acceleration of the elevator is downwards and therefore negative. The overall acceleration of the man is downward with the the direction of the elevator meaning that ma is negative. The external forces acting on the man are the force of gravity acting downwards (-W=-mg) and the supporting...
  24. Frouel

    How can I solve this physics problem step by step?

    I attended to many attemps and I not able to find out no dependencies in this layout. Does someone can show me how to solve this problem step by step? What we must take into considarion in solving such tasks?. How to start?. I got stuck. This task is from Polish Physics Olympics.
  25. Hamiltonian

    The leaning ladder problem using Newtonian mechanics

    $$ R - f = m\ddot x$$ $$N - mg = m\ddot y$$ were N and R are the normal reactions from the smooth wall and rough ground. and f is the friction provided by the ground. $$ f = \mu N = cot(\phi)N/4$$ i tried to formulate a constraint relation between ##\ddot x## and ##\ddot y## so that I could...
  26. wolfy

    B Simulators for Quantum Mechanics

    A member helped me discover a new quantum tunneling sim online, it's free and quite amazing to look at. https://phet.colorado.edu/en/simulation/quantum-tunneling Are there any other more advance simulators on the net and would anyone like to discuss this program with me as I am new to Quantum...
  27. R

    Quantum What Book Best Explores Quantum Mechanics for Conceptual Thinkers?

    Hi everyone , I am interested in learning quantum mechanics. I want to read a book which explains each and every aspect of quantum physics , gives a conceptual understanding with the help of logical thinking. Also it should be like that if I know the most basic theory and...
  28. J

    Launching a projectile to hit a target moving away from the launch point

  29. aspodkfpo

    Weird algebra and logic in a mechanics cart quesiton

    Logic and equations seem to have come out of nowhere in this question. I have been unable to understand where these equations come from and why they are used. Can someone describe the logic for the steps in the question?
  30. Another

    Classical Mechanics: Why can we cancel the derivative of dt from these equations?

    problem in this book : classical mechanics goldstein Why can we cancel the derivative of dt from these equations? e.g. ##\frac{d(x)}{dt} + \frac{b sin\theta}{2} \frac{d(\theta)}{dt} = asin\theta \frac{d(\phi)}{dt}## ## x +\frac{b \theta sin\theta}{2} = a \phi sin\theta ## because I think...
  31. Like Tony Stark

    Conservative forces vs friction

    Hello I've written that homework statement as an example to illustrate my doubt: How can I tell if a force is conservative or not? I've read that, if the curl of the force is 0, it's conservative. But what about the friction force (##f=\mu N##)? Its curl is also zero, but it's not conservative...
  32. Z

    Landau vol.1 Mechanics: Expansion of L' and Dependence on Velocity

    Let ##K## and ##K'## be two inertial frame, If K is moving with infinitesimal velocity relative to ##K'## , then ##v' = v + \epsilon##. Note that ##L(v^2) - L(v'^2)## is only a total derivative of a function of coordinate and time. (I understand this part) Because ##L' = L(v'^2) = L(v^2 +...
  33. aspodkfpo

    Chocolate milk mechanics question

    https://www.asi.edu.au/wp-content/uploads/2018/07/ASOE_2017-Physics-solutions.pdf Question 11 b) I don't see why they ignore the white milk in the middle in their model. Nor do I understand how they get that the white milk is also traveling at U. As for the rest of the algebra, there's no need...
  34. Z

    On Landau vol.1 Pg.5 (Question about conclusion drawn by Landau)

    I understand that d/dv(L) = constant, and L is only dependent on v, but how do we get to the fact that v = constant?
  35. draculamedula

    I How do I determine I for a truncated cone in the bending of a Stylus Shaft?

    So I have a Stylus as shown in above fig. Fixed at Point A, Force (F) is applied perpendicular to the stylus axis. How do we find deflection at the end of the Stylus (Made of Two Different Materials as shown in the figure)? Hand Calculations are much appreciated. Thank you.
  36. M

    Engineering Fluids mechanics homework, feel like I have messed up the equations

    Edit: So I have written out equation 3 again and taken a picture to show my working out, the 2 things that I am confused about is how do I find the coefficient of viscosity? I know that syrup is high viscosity and water is low viscosity but I don't know the equation to get the actual value. The...
  37. S

    Question about Particle disintegration (Landau mechanics page 43)

    On page 41 for the spontaneous disintegration of a particle into two, Landau states the total momentum in the C system is zero. On page 43 for the disintegration of many particles into two, Landau states: In the C system... every resulting particle (of a given kind) has the same energy... I...
  38. B

    Choosing proper coordinates in a complex 2 pulley system

    FBD Block 1 FBD Block 2 FBD Pulley B I'm mainly concerned with the coordinate system direction in this problem, but just to show my attempt, here are the equations I got from the system. ##-T_A + m_1g = m_1a_1## ##T_B - m_2g = m_2a_2## ##T_A - 2T_B = 0## Using the fact that the lengths...
  39. enthusiast

    Mechanics: A bowling ball is thrown and rolls with slipping

    Summary:: A bowling ball is thrown on a bowling lane with the coefficient of friction ##\mu## with an initial velocity of ##v_0## and no rotation. After hitting the ground, it starts rolling with slipping. After how much time after hitting the lane will the ball stop slipping? What will be its...
  40. A

    How to Grow a Sustainable Garden""Growing a Sustainable Garden: Tips & Tricks

  41. B

    Direction of acceleration of a projectile with drag force

    First and foremost, thank you so much for your help! I'm new to Physics Forums, and this is my first post. I thought I understood the problem, but as I moved on to the subsequent parts of it became apparent that I was missing something. I set up my ##F = ma## equation as below, and solved that...
  42. burian

    Trajectory of a mass element in a string overhanging a pulley

    Hello everyone, this is a thought experiment I made, it involves two ropes being pulled of a pulley similar to an atwood machine, and a block attached to the two pulleys at the other end. The ropes are being pulled at a constant velocity $ U$ from the end away from the block and the block rises...
  43. Vivek98phyboy

    What am I Missing? Solving Conservation of Energy

    By solving conservation of energy, I was able to find the linear velocity which is [10g(H-R-Rsin(theta))/7]^½ and by differentiating this with respect to "t", I arrived at the tangential acceleration value of -(5gcos(theta))/7 and found it to be in agreement with the solution provided in the...
  44. Leo Liu

    Questions about infinitesimal changes in a mechanics problem

    While reading Kleppner's book, I came across the question above whose solution given by an answer book, is shown below. I wrote out an equation for inward force and another equation for horizontal forces: $$\begin{cases} f_{\Delta \theta}=\mu N=\mu \frac{\Delta\theta} 2 (T+T'),\text{ where T'...
  45. redtree

    I Relativistic quantum mechanics

    Given that the Minkowski metric implies the Lorentz transformations and special relativity, why do the equations of relativistic quantum mechanics, i.e., the Dirac and Klein-Gordon equations, require a mass term to unite quantum mechanics and special relativity? Shouldn't their formulation in...
  46. R

    I Consciousness and quantum mechanics

    Reading book, “God? Very Probable”. The author quotes Wigners comments in his book, “Remarks on the Mind- Body Question” 169, 171, 173. “The very study of the external world led to the conclusion that the content of consciousness is an ultimate reality. Given the ultimate priority of...
  47. J

    Why is there angular acceleration in a non-spinning gyroscope?

    I was watching the above video which is part of a series explaining the mechanics behind a gyroscope. In the video the author explains the mechanics of the gyroscope when stationary (the disc is not rotating). Here he derives a result that the angular acceleration is g/r which is non zero...
  48. G

    Mechanics Circular Motion Question

    Part (i) *Pink represents mark scheme method Part 2 However I am still confused on the diagram.
  49. Leo Liu

    Insight into polar coordinates (Newtonian mechanics)?

    I am learning to use polar coordinates to describe the motions of particles. Now I know how to use polar coordinates to solve problems and the derivations of many equations. However, the big picture of polar coordinates remains unclear to me. Would you mind sharing your insight with me so that I...
  50. I

    Studying What should I work on next? (Introductory Mechanics)

    I have taken AP Physics C: Mechanics during this past semester. Due to COVID-19 my teacher decided to not teach us the last unit that usually covered gravitation and simple harmonic motion since it was not going to be on the AP exam. For this reason I will be taking intro mechanics again in...
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