What is Classic physics: Definition and 38 Discussions

Classical physics is a group of physics theories that predate modern, more complete, or more widely applicable theories. If a currently accepted theory is considered to be modern, and its introduction represented a major paradigm shift, then the previous theories, or new theories based on the older paradigm, will often be referred to as belonging to the realm of "classical physics".
As such, the definition of a classical theory depends on context. Classical physical concepts are often used when modern theories are unnecessarily complex for a particular situation. Most usually classical physics refers to pre-1900 physics, while modern physics refers to post-1900 physics which incorporates elements of quantum mechanics and relativity.

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1. I Deriving formula for kinetic energy

Hello! I am new to the differential version of classical physics, and I am trying to work how to derive kinetic energy from some pre-assumed equations: Assume that we know: ##\ddot{z} = 0## and ##m\ddot{\textbf{r}} \cdot \dot{\textbf{r}} = 0##This results in \frac{1}{2}m\dot{r}^2 = W =...
2. Self-teaching Physics 1, 2, and 3 using MIT Open Courseware

Hi, I am trying to teach myself Physics 1, 2, and 3. I tried learning using MIT Open Courseware. The courses which I tried taking are 8.01, 8.02, and 8.03. Are these courses in MIT Open Courseware a complete college course or just a brief overview of online courses in physics, as the video is...
3. I Does gas flow from low to high pressure?

Here's a grab at 1:50 from the Bernoulli's Principle Demo: Venturi Tube video It appears to show the air flowing from the viewer's right to left where the pressure in the third manometer appears to be higher than in the middle one. Is there some complexity from the manometers being...
4. Gas temperature in a constant volume

An insulated container (constant volume, adiabatic) contains an Ideal gas with pressure P1 and temperature T1. We open the container's hatch for a few seconds and let some particles escape from the container, then we close the hatch again. We know container's pressure has reduced by exiting...
5. I When does the instantaneous velocity exist?

The instantaneous velocity at time a is defined as derivative of motion function f(t). It is not similar to average velocity in an interval of time. From the Newton law. If an object is at rest, we must exert a force to make it move, assume that there is no friction. Depend on the weight of...
6. I What friction causes objects to decelerate?

When I exert enough force that overcome the static friction. The object start moving and surface create kinetic friction on object if I exert harder overcome the maximum of friction it start accelerate. When I release the object will the kinetic friction disappear immediately proportional to...
7. Maximum bending moment and maximum deflection of the spring?

How can I find the maximum bending moment and maximum deflection for a spring? It would be very helpful if you could explain the specific procedure and formula in an easy-to-understand manner. that's all, thank you very much.
8. I Classical analogy approach to quantum mechanics

I have read about several approcahes to bypass some classical restrictions to quantum facts such as the electron being in a torus-like shape to avoid ,the greater than speed of light, rotation paradox . Could you recommend websites , sources or books that give good classical analogy to quantum...

10. Intro Physics Searching for a Classic Physics Textbook with Autostereograms

Perhaps this is a fever dream, but I seem to recall a classic Physics textbook that had illustrations of 3D vectors using autostereograms. However, I can't remember which one (or find any evidence that I'm not making this up). I also have the notion that this was very early, well before the...
11. B Can you use hand tools on the moon?

No, this isn't a homework question. I'm genuinely curious; If I were to magically teleport and happenstance with a shovel and survive the harsh climate, could I use said shovel? Maybe hand drills? I would assume the shovel would be a class one lever, and thus the moon's lower gravity would...
12. The sources of error in a diffraction grating experiment

In a diffraction grating experiment, what can be the sources of error and also what effect do these sources have on the unknown quantity (wavelength) in the experiment?
13. I Understanding Action as a Scalar: Exploring the Concept and its Importance

Why is the action a scalar? Please explain.
14. B Why one substance does not pass through another substance？

1. Books and desks have only one atomic core There is a book and desk, suppose the book and desk are composed of atomic atomic core and extranuclear electrons. Now, the book moves down along the y axis, while the desk stands still or moves up. Now there is a problem: the position of the...
15. B What is Energy? A Clear Definition and Explanation

Hello there, I have heard countless times about the word energy, but I still don't know what exactly an energy is. Like for example, we know the definition of a physical quantity called velocity which by definition is change in displacement (so we can easily describe what a velocity is). We...
16. Estimate the initial velocity of the cars after the collision

What came to my mind for this question is: Consider one of the cars. The velocity and mass of this car are V and M respectively. And the velocity and mass of the piece attached to the car are m, v respectively. Before the collision, the velocity of this piece relative to this car is zero. So its...
17. How to find the frequency of the second wave?

I don’t understand how to approach this. So I couldn’t make an attempt at a solution. Please help me understand better. Thank you in advance.
18. Power spent to keep a spring compressed

I was wondering, I have an engine that should keep a spring compressed. How can I calculate the power necessary for this? The work is Force x Distance, as there is no distance, there is no work, so no power... But obviously to keep the spring compressed the engine will have to produce a...
19. Hard time with this Vector Velocity Problem

Summary: I've posted this in a few forums but still confused on this problem. If the plane is moving at 200km/h and the wind pushes the plane with a velocity of 85km/h, then the resultant velocity would be 217km/h, and using sine inverse, 217.sin(theta=85, I got 23°, which is B, but the answer...
20. Clearing a wall with a golf shot

Every trajectory follows a parabola if we neglect air resistance. So we can calculate the maximum distance in x direction s_max. Also we can determine the time it takes to hit the ground again t_max. If the ground is everywhere the same height, I can assume that at t_max/2 the height (s_y) is at...
21. I What is the tangential component? Taylor p.347

I do not understand why the tan component for a gravity affected by the centrifugal force: g = Ω^2 * R * sinθ * cosθ So I tried to draw this: using a "big" X-shaped axis where the / component goes along the main gravity direction while \ points normal to / this direction. Then the centrifugal...
22. Does the spin angular momentum count?

Taking the Earth orbiting the sun as an example, when I consider the angular momentum of the Earth about the sun, should the spin angular momentum be counted? I'm confused that if it's counted, the spin angular momentum, Lcm=Icm×ωspin, is different from other angular momentum regarding the...
23. Classical A good book that covers everything?

Hello! About Me: I'm an Electrical And Computer Engineer under graded student. The only physics we learn in the University in which I'm enrolled is Electromagnetics and nothing more. Well in high school we learned Classical Physics but i don't remember anything (Except some of Newton's motion...
24. What is the equation for friction's role in walking?

When we loose the touch with ground no friction is acting..so how we accelarate ? also friction prevent our foot from sliding but also accelarates our body ? how is it possible to acting in 2 different points ( foot and center of mass ) ?
25. B What we mean in physics definition (quantity or property)?

Many books sometimes for example define energy as quantity and sometimes as property. Also the definition of energy is the ability to do work or the meter of the ability to do work ? we define for example force as a quantity or as some quality and then we quantify this ?
26. Force needed to push a trolley onto sidewalk

Homework Statement Find minimum Force needed to push the trolley onto the curb. Homework Equations Torque=r x F The Attempt at a Solution The front wheel will rotate about point b if the trolley is pushed onto the sidewalk. This should mean that as soon as the wheel has a positive torque...
27. Question on classical electron radius

Hi at everyone, why on wiki there is written: " According to modern understanding, the electron is a point particle with a point charge and no spatial extent. Attempts to model the electron as a non-point particle are considered ill-conceived and counter-pedagogic " I don't understand this...
28. S

I Calculating the Force of a Planet Using Energy and Radius

I want to ask if we now the energy of a planet (mc2) and we divided that energy over the radius(R) of that planet what kind of force(F) we get --> mc2/Radius = F(?)
29. Better textbook for analytical mechanics

Hi at all. According to you which of the two texts, between Landau-Lifshitz (mechanics) and the Goldberg (classical mech) is better for study Analytical Mech ? Or there are other better ones ?
30. Question about torque and center of mass

Supposing that we have a hollow sphere of mass m and radius R. Furthermore, suppose that we attach the sphere to a rod of length L and mass M. Now, suppose we rest the rod-sphere contraption on a pyramid a distance (X+R) from the center of mass of the sphere and a distance [(L/2)-X)] from the...
31. Question about studying statistical mechanics before or after MQ?

Hi i would like to understand if it is advisable to study statistical mechanics before of the MQ (with the classical stat. mec.), or after the MQ all together ?? Thank you
32. I What Is the Formula for the Position of a Mass Falling Towards a Planet?

Question: Finding the closed formula s(t) that gives the approaching position of an inertial mass to a planet Supposing the mass initially stationary, and far enough and for long enough that it is NOT possible to consider the gravity as constant while it moves closer and closer. Said in a...
33. Transforming to a Rotating Reference Frame

Homework Statement Let ## \mathbf{r} ## be the position of a point in a rigid body relative to some origin ##O##. Let ##\mathbf{R}## be the position of the centre of mass from that origin. ##\mathbf{r^{*}} = (\mathbf{r}-\mathbf{R})##. ## d\boldsymbol{\phi} ## is the infitesimal vector directed...
34. Friction of rubber box on concrete floor

Homework Statement A 10 kg rubber box is resting on a concrete floor. A force of 200 N is then applied to this box in a horizontal direction. What is the magnitude of the friction force on the box? Homework Equations This is a question about applying Newton's laws so Fsmax = μs η and η = mg...
35. Intro Physics Need help remembering a classic Physics books

Hello. I am new here and I registered because I just can´t remember a book I studied long time ago. Is an introductory Physics book used in colleges and universities. The book is well known, I would say the author is famous. I'm 90% sure the author surname begins with "f" and is not Feynmann. I...
36. Interesting solutions to classic physics problems

From time to time I hear about people coming up with creative/"non-mainstream" solutions to classical physics problems, whether by looking from a very different angle or using some unusual math that's unknown to anyone but that one slightly quirky professor from faculty of mathematics. However I...
37. What Are the Classic Problems of Physics?

The "Classic" Physics Problems. In my physics education/career I have often heard people refer to the "classic" such and such a problem or to the "typical" or "archetypal" physics problems. These are the problems/models that many/most university physics problems seem to reduce down to, no...
38. Does This Defy Classic Physics?

Maybe i am looking at things wrong, but it seems that classic physics cannot tell me how much gravitational energy an object has at "rest", when it is at the ground potential- at zero. Example. I have a table. I place a 100 kg object on the table. What is the gravitational energy of the...