Mechanics Definition and 999 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. 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.
  2. 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...
  3. 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...
  4. 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...
  5. J

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

  6. 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?
  7. Another

    Can We Cancel the Derivative of dt in 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...
  8. 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...
  9. 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 +...
  10. 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...
  11. 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?
  12. 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.
  13. 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...
  14. 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...
  15. 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...
  16. 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...
  17. A

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

  18. 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...
  19. 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...
  20. 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...
  21. 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'...
  22. 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...
  23. 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...
  24. 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...
  25. G

    Mechanics Circular Motion Question

    Part (i) *Pink represents mark scheme method Part 2 However I am still confused on the diagram.
  26. 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...
  27. 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...
  28. tanaygupta2000

    Electrons impinging on a crystal

    Since the crystal spacing is given to be 0.4 nm, so d = 0.4 nm = 4e-10 m in Bragg's law formula For θ = 90° & n = 1, I got λ = 2d = 8e-10 m Using this value in De-broglie wavelength, I got p = h/λ = 8.28e-25 Now kinetic energy of the electrons is given by E = p^2/2m Using value of p, I am...
  29. Selfphysicslearner

    What is wrong with following physics equations? (velocity and acceleration)

    vavg=(Vi+Vf)/2 vavg=h/t then vavg*t=h h=(Vi+Vf)/2 * t Vf=at (Vit+at2)*1/2=h But formula on every resource I found says it should be; (Vit+at2*1/2)=h What mistake did I do ?
  30. John100861

    David Morin classical mechanics Problem 2.6: Disk held up by a massless string

    The first part is easy, we have 2T= Mg T= 0.5 Mg Now for the second part where I'm having trouble understanding Morin's solution: I take the normal force on a small circle arc to be N, we know that the y component of the normal force must be balance with Mg for the whole disk, therefore Ny =...
  31. Nexus99

    Cylinder inside a cylindrical track

    1) Conservation of energy ## mg(R-r)(1-cos \theta_0) = \frac{1}{2}mv^2 + \frac{1}{2} I \omega^2 ## because of pure rolling ## \omega = \frac{v}{r} ## So i got: ## v = \sqrt{\frac{4}{3} g (R-r) (1-cos(\theta_0))} ## this is how i got normal force: 2) ## N - mg = m \frac{v^2}{R-r} ## where v is...
  32. Nexus99

    A falling rotating rod strikes a ball of mass M....

    A homogeneous rod of length l and mass m is free to rotate in a vertical plane around a point A, the constraint is without friction. Initially the rod is stopped in the position of unstable equilibrium, therefore it begins to fall rotating around A and hits, after a rotation of ## \pi ## , a...
  33. S

    Classical Supplement to Classical Mechanics by Goldstein

    Are there any lecture notes that closely follow Classical Mechanics by Goldstein? I am asking this since I am seeing some comments in this forum that it contains some conceptual errors, e.g. nonholonomic constraints. If there is a book that "closely" follows Goldstein, it will be good too.
  34. AlonZ

    Mechanics- Conservation of energy

    My, supposedly rational thought is that if the pendulum will drop from a height higher than the top of the loop's height, by the law of conservation of energy, it'll have enough velocity to complete the loop. The teacher's final result shows a different approach. Am I right? Wrong? Thanks
  35. RemotePhysics

    Futher Mechanics: Circular Motion of a Car Going Around a Banked Turn

    Below is my working out. If you could have a look at my answers and see if they are correct and then advice me on how to improve my solutions for Parts I and II, and how to answer F and G with the given information. Thanks in advance! Parts aand b are diagrams so please refer to the attached...
  36. G

    Mechanics: Angular Velocity Vector Questions

    Answers are the following : (i) v=(2cost)i - (2sint)j -(1/2)k (ii)2.06m/s (iii)2m/s^2 horizontally towards the vertical axis, making an angle of pi/4 with both the I and j axes.
  37. core1985

    Which system of units is coherent for mechanics?

    So, should i write All of these as accodring to wiki pedia maxwell applied coherence concept to FPS, CGS, and SI is already coherent so answer will be All of these ?? Am i right or MKS because question is restricted to mechanics only ?
  38. P

    Tackling a Classical Mechanics Problem at Pisa University

    This problem is hard. It found it listed among problems discussed in a classical mechanics course for physicists at the university of Pisa and don't have a full solution. It's not 100% guaranteed that there's a nice close-form solution, but probably yes; and if not, there should be some trick to...
  39. D

    Equations of motion of a system with non holonomic constraints

    Hello, I have a system with 2 degrees of freedom with 2 non-holonomic constrains that can be expressed by:##A_1 dq_1 +Cdq_3 + Ddq_4 = 0## ##A_2 dq_1 + Bdq_2 = 0##Being ##q_1, q_2, q_3## and ##q_4## four generalized coordinates that can describe the movement of the system. And ##A_1, A_2, B...
  40. bob012345

    I Is Quantum Mechanics Infinitely More Complex than Classical Mechanics?

    Please critique this text. It came from a research article* I found but I'm only interested if the sentence is 100% accurate or not and not in the specifics of the article itself. Are they suggesting Hilbert space is always infinite? Thanks. Quantum mechanics is infinitely more complicated than...
  41. LuccaP4

    Hamiltonian mechanics: phase diagram

    The issue here is that I don't know how to operate the final equations in order to get the phase diagram. I suppose some things are held constant so I can get a known curve such as an ellipse. I attach the solved part, I don't know how to go on.
  42. A. Neumaier

    I Steven Weinberg on the interpretation of quantum mechanics

    I think Weinberg is quite clear about this: On p.87 of the second edition of his quantum mechanics book, he says, and on p.88: After having discussed decoherence, he says on p.92: For the instrumentalist approach (apparently your view of the matter), he states on p.92f this drawback: Then...
  43. S

    Quantum What are the best books for: 1.Mass 2.Energy and 3.Quantum Mechanics?

    What are the best theoretical books I can study for understanding the basic as well as advanced; mass, energy and quantum mechanics.
  44. L

    Dispersion relation statistical mechanics

    I know that this is the general case of the Einstein and Debye Model.
  45. G

    I How does Bohmian mechanics explain quantum bomb testing?

    Hi. In an Elitzur–Vaidman bomb tester, will the guiding wave be different in a situation with a live bomb compared to one with only a dud? And if yes, how does the bomb interact with the guiding wave? Because usually it is described as a pointlike device that only explodes when hit by the...
  46. LuccaP4

    Lagrangian mechanics: central-force-like problem

    I copy again the statement here: So, I think I solved parts a to c but I don't get part d. I couldn't even start it because I don't understand how to set the problem. I think it refers to some kind of motion like this one in the picture, so I'll have a maximum and a minimum r, and I can get...
  47. PGaccount

    I Partition function of quantum mechanics

    In quantum mechanics, we have the partition function Z[j] = e-W[j] = ∫ eiS+ jiOi. The propagator between two points 1 and 2 can be calculated as ## \frac{\delta}{\delta j_1}\frac{\delta}{\delta j_2} Z = \langle O_1 O_2 \rangle## The S in the path integral has been replaced by S → S + jiOi...
  48. J

    MHB Engineering Mechanics: airplane landing

    The landing speed of an airplane is 360 kph. When it touches down, it puts on its brakes and reverses its engines. The retardation in its speed is 0.2 times the square root of its speed. Determine the time elapsed in seconds from the point of touchdown until the plane comes to a complete stop.
  49. J

    MHB Engineering Mechanics: car speeding up

    A car starting from rest picks up at a uniform rate and passes three electric post in succession. The post are spaced 360 m apart along a straight rod. The car takes 10 seconds to travel from the first post to the 2nd post and tales 6 seconds to go from the 2nd post to the 3rd post. Determine...
  50. J

    MHB Engineering Mechanics: depth of crater

    The depth of the crater of the Taal volcano was calculated in the following manner: From a helicopter flying vertically upward at 6m/s. A small bomb was released at the instant the helicopter was 20m above the crater surface. The sound of explosion was heard 9sec later. If the speed of sound is...
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