What is Circular: Definition and 1000 Discussions

A circular economy (also referred to as "circularity") is an economic system aimed at eliminating waste and the continual use of resources. Circular systems employ reuse, sharing, repair, refurbishment, remanufacturing and recycling to create a closed-loop system, minimising the use of resource inputs and the creation of waste, pollution and carbon emissions. The circular economy aims to keep products, equipment and infrastructure in use for longer, thus improving the productivity of these resources. Waste materials and energy should become input for other processes through waste valorization: either as a component or recovered resource for another industrial process or as regenerative resources for nature (e.g., compost). This regenerative approach is in contrast to the traditional linear economy, which has a "take, make, dispose" model of production.In recent years, concepts based on (re-)cycling resources are increasingly gaining importance. The most prominent among these concepts might be the circular economy, with its comprehensive support by China and the European Union. There is also a broad range of similar concepts or schools of thought, including cradle-to-cradle laws of ecology, looped and performance economy, regenerative design, industrial ecology, biomimicry, and the blue economy. These concepts seem intuitively to be more sustainable than the current linear economic system. The reduction of resource inputs into and waste and emission leakage out of the system reduces resource depletion and environmental pollution. However, these simple assumptions are not sufficient to deal with the involved systemic complexity and disregards potential trade-offs. For example, the social dimension of sustainability seems to be only marginally addressed in many publications on the Circular Economy, and some cases require different or additional strategies, such as purchasing new, more energy-efficient equipment.

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  1. S

    Inclusion-Exclusion Principle and Circular Arrangement

    6 people are invited to a dinner party and they are sitting on a round table. Each person is sitting on a chair there are exactly 6 chairs. So each person has exactly two neighboring chairs, one on the left and the other on the right. The host decides to shuffle the sitting arrangements. A...
  2. D

    Hydrodynamic Entry Length of Flow Through Circular Annulus

    I might be going crazy or searching at the wrong places. Is there an empirical formula for solving the hydrodynamic entry length of laminar flow through a circular annulus? Thanks!
  3. tomo

    2 questions regarding circular motion and Newton's 1st Law

    Hey, I'm an adult who finally realized that physics is great and tries to recall (or rather learn for the first time) what he learned at the school. I've been reading some basic things around. It's not really a homework question, I'm just trying to understand the laws here. 1. I know that if a...
  4. T

    How does kinetic energy change in circular motion?

    Could someone explain to me how the kinetic energy of a body moving in a circle is like? I got tempted it stays constant as the speed is constant but that turned out to be false. I am interested in places where the body is at top, side and bottom and so on. So I'd like to also know what the KE...
  5. L

    Parametric equation of a particle in a circular trajectory

    Homework Statement [/B] You are given a particle, with the trajectory of a circle, with radius of 3 meters. The particle moves clock-wise, and when t=0, the x, y coordinates are (0, -3). Find parametric equations for the coordinates (x, y) in terms of the parametric t (time). Homework...
  6. A

    Why they don't give me the same answer? dynamics of uniform circular motion

    Homework Statement So a body $m$ is on a uniform circular motion ($\omega = d\theta/dt = \text{constant}$), it is suspended by an inextensible rope with negligeable mass Homework Equations P = mg , didnt know what to put here The Attempt at a Solution So this is what the book did. What I...
  7. S

    Circular Motion and Gravitation of tether ball

    Homework Statement There is a tether ball swinging around in a uniform circle on a rope that is 1.90m long. Marcus hit the ball so hard that the string holding the ball made a 20.0 degree angle to the horizontal. What is the tension in the rope if the ball has a mass of 1.40 kg? Assume that the...
  8. A

    Force Exerted Non-Uniform Circular Motion

    Homework Statement A bucket of water (10kg) is swung vertically. Radius is 1 m. It takes 1 second to spin the bucket in a full circle. a. How much force has to be exerted at the top of its motion? b. How much force must be exerted at the bottom? Homework Equations vtop=sqrt(gr) top: Ftension=...
  9. F

    Calculating Speed in Circular Motion: A Roller Coaster Conundrum

    A 400kg roller coaster cart travels along the inside of a vertical circular track of radius 10 m. At its highest point it moves at 20 m/s. Friction between the cart and track is negligible. Find the cart's speed one quarter of a loop later (when it's at the same height as the loop's center). I...
  10. Mickey Tee

    Vertical Circular Motion Problem

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  11. cseil

    Uniform circular motion for proton and 2 particles

    [Note by mentor: This thread does not use the homework template because it was moved here from a non-homework forum.] Hello, I have a problem with this exercise. I don't know if my solution is right! Could you check it, please? A proton with kinetic energy Kp is moving in a uniform magnetic...
  12. Ludwig

    Uniform Circular Motion puzzle

    The position function for a particle moving on a circle (with constant speed) is: ## \vec{r}(t)=\left \langle r\,sin(t), \, r\,cos(t) \right \rangle ## Taking the first and second derivatives, ## \vec{v}(t)=\left \langle -r\,cos(t), \, r\,sin(t) \right \rangle ## ## \vec{a}(t)=\left \langle...
  13. F

    Circular Motion using polar coordinates - Mechanics

    Homework Statement A block of mass M is on a frictionless table that has a hole a distance S from the block. The block is attached to a massless string that goes through the hole. A force F is applied to the string and the block is given an angular velocity w0 , with the hole as the origin, so...
  14. S

    Confused in diffferent forces involved in circular motion

    Hi, I am trying to solve one problem of circular motion and I searched on Internet and found many things and I am confused about different forces or I think same force is shown as different symbol. What I learned is as follows:Force = F = ma (horizontal movement - where height is not involved)...
  15. S

    Circular motion banked curve questions

    Relative equations: F = ma a = v^2/r Fcent = mv^2/r ωf^2 – ωi^2 = 2αs s = θr ω = v/r Problem statement and work so far are all included: (I am having trouble with 5 and no clue how to start on 7-9) You are designing a roadway for a local business, to include a circular exit ramp from the...
  16. K

    High school circular motion problem

    Homework Statement The problem is: An amusement park is replacing it's stand-up roller coaster with a G-Force ride. Riders will enter the ride at the apex and lean against the wall of the ride. The G-force ride will speed up until riders reach height h above the apex. Determine the minimum...
  17. F

    Circular Motion Ball on a String

    Homework Statement https://www.dropbox.com/s/slpu1p8jplmxzmy/Screenshot%202014-11-18%2020.11.58.png?dl=0 Homework Equations Fnet = ma ma = (mv^2)/r The Attempt at a Solution ai) Ft up, mg down /\Ft I m I \/mg aii) both down m I I \/mg \/Ft aiii) Ft right, mg down m - >Ft I \/mg b)...
  18. LarryS

    Classical Circular Polarization vs. Photon Spin Eigenstates

    Hello, Given an electromagnetic wave that is, from a classical point-of-view, not circular polarized. Does that correspond in QM to photons with the ZERO spin eigenstate? Thanks in advance.
  19. Adithyan

    Particle inside a smooth groove performing circular motion

    Homework Statement [/B] A circular table of radius rotates about its center with an angular velocity 'w'. The surface of the table is smooth. A groove is dug along the surface of the table at a distance 'd' from the centre of the table till the circumference. A particle is kept at the starting...
  20. T

    Circular Motion with time-dependent radial acceleration

    Homework Statement A particle is traveling on a circle with a radius R. The particle's radial acceleration is given as: a_r=At^4 At time t=0 the particle is at (R,0) . A. Find the distance that the particle has traveled as a function of time S(t) . B. Display the particle's acceleration...
  21. P

    Horizontal circular motion problem

    Homework Statement I have this question to solve for homework : " An object of mass 10 kg is whirled around a horizontal circle of radius 4m" If the uniform speed of the object is 5m/s Calculate a) tension in string b) angle of inclination of string to the vertical.Homework EquationsThe Attempt...
  22. D

    Circular Motion -- Swinging keys on a string in a vertical circle

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  23. Hijaz Aslam

    Electric Field of a circular arc at a point

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  24. S

    What is the question you are trying to answer?

    Homework Statement Hello there, So I have a problem that I can't seem to figure out on my own. I have no background in physics (I haven't taken a physics course as of right now,) but my robotics team requires some math. I need to find the equation for moving something with a mass of 1.5kg...
  25. T

    Hydrostatic Pressure on Curved Circular Surface

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  26. A

    Vibrations of a circular membrane with free ends

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  27. P

    Uniform Circular Motion on a race track

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  28. P

    Uniform Circular Motion of a centrifuge

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  29. P

    Non-uniform circular motion problem

    Homework Statement A 200g ball on a 55-cm-long string is swung in a vertical circle about a point 200 cm above the floor. The string suddenly breaks when it is parallel to the ground and the ball is moving upward. The ball reaches a height 600 cm above the floor. What was the tension in the...
  30. G

    Uniform Circular Motion of a Spherical Earth

    Homework Statement In this question, the Earth is modeled as a uniform sphere of radius 6400km. Objects are released from points just above the Earth's surface at the equator and at the North Pole. Which will fall to the Earth with the greater acceleration and by how much? Homework Equations...
  31. N

    Circular motion of a steel block

    Homework Statement A .5 kg steel block rotates on a steel table, attached to a 1.20m-long hollow tube. Air is fed through the tube and is ejected from the block, giving it a thrust force of 5.21N perpendicular to the tube. Max tension the tube can withstand without breaking is 50N. Assume...
  32. E

    The Impact of Current on Circular Paths: Examining Equation 1

    Homework Statement Once a circular path has been obtain for the electrons, how will increasing current to the coils affect that path? Use equation 1 and the fact that e/m is a constant for the electron. Homework Equations e/m = 2V/B^2r^2 The Attempt at a Solution I'm unclear as to how to...
  33. K

    Circular Motion of a moving rock Problem

    Homework Statement You hold a bucket in one hand. In the bucket is a 480g rock. You swing the bucket so the rock moves in a vertical circle 2.8m in diameter. What is the minimum speed the rock must have at the top of the circle if it is to always stay in contact with the bottom of the bucket...
  34. Quadrat

    Maximum angle in a vertical circular motion

    Homework Statement A person with the mass m swinging in a pendulum motion (vertical circular motion) hangs by a rope (with negligible mass) that can stand a tension of two times the person's mass. I am trying to calculate the maximum angles of the circular motion without the rope breaking...
  35. gcombina

    Circular Orbit / Practice Quiz #4, Question 27

    Homework Statement What is the acceleration due to gravity at an altitude of 1.00 x 10^6 above the Earth's surface, given that the radius of the Earth is 6.38 x 10^6 m?Homework Equations Using g = GMm/r^2 Fc = mv^2/r The Attempt at a Solution Fc = mv^2/r How can I solve this equation if I am...
  36. D

    Calculating Fourier Transform in Circular Wells

    Hi everyone, do you know how to calculate the Fourier transform for the infinitely deep circular well (confined system)? The radial wave function is given by R=N_m J_m (k r). k=\alpha_{mn}/R. R is the radius of the circular well. R(k R)=0. Thanks. Another question is that The k in J_{m}(k r)...
  37. P

    Does the observable universe support the idea of circular math?

    so, i am wondering, the math equation for a circle, we can prove it has infinite number of points, thus no sides, but that's on paper. is there anything in observable universe that shows us this math??
  38. A

    Velocity of an Object in Uniform Circular Motion

    Homework Statement An object of mass 0.5 kg is swung in uniform circular motion. The radius is 2 meters, and the force exerted is 4 N. Calculate the magnitude of the velocity. Answer Choices: a) 0.25 m/s b) 1 m/s c) 4 m/s d) 16 m/s Homework Equations v = 2piR/T F = mv^2/R The Attempt at a...
  39. P

    Uniform Circular Motion: Why is the velocity changing?

    I encountered this question in a practice test for an upcoming exam. My first inkling was to answer with (C) because in uniform circular motion, the acceleration always points towards the center of the circle, but the actual answer was D. Do you think this question was just an issue of direction...
  40. D

    Finding acceleration with circular motion

    Homework Statement Entrance and exit ramps for freeways are often circular stretches of road. As you go around one at a constant speed, you will experience a constant acceleration. Suppose you drive through an entrance ramp at a modest speed and your acceleration is 2.0 m/s2. What will be the...
  41. J

    Circular Motion: Constant Centripetal Force and Velocity

    Homework Statement Assessing the required forces at the top and bottom of a loop de loop. I understand that you need a larger force at the bottom of the loop because you have to counter gravity. My question is, when you are undergoing uniform circular motion and your centripetal acceleration is...
  42. B

    Minimum Shear Stress in Hollow Circular Tube

    Homework Statement A hollow pipe has an inner diameter of 80 mm and an outer diameter of 100 mm. If its end is tightened using a torque wrench using 80 N forces, determine the maximum and minimum shear stress in the material. Where are they located? Note: In the diagram of the picture, the...
  43. avinamaurya

    Circular polarization phase difference

    Phase difference between two component of Electric field vector seems to me that the phase difference for circular should be of odd multiples of 90 but its not 90 when n value substituted. Please help for solution..
  44. T

    Vertical and horizontal circular motion: How to identify the centripetal force?

    I made notes on this in class, but I did not understand everything about it. So, what I know is that vertical motion is when the object goes around in a circle like this: And horizontal I guess it is like this: But then I am very confused regarding what my teacher told me for horizontal...
  45. J

    Circular Motion - Banked Turns

    Homework Statement Please could someone help explain the case of a friction-less banked race track. If you take an Olympic indoor banked cycle track and imagine for a moment that it was friction-less. The laws of circular motion tell us that without friction the banked geometry can enable a...
  46. R

    Frictional Force in Circular Motion

    Hi Guys, I am trying to understand that how does the frictional force on a car moving in a circle is directed towards the centre? I do understand that kinetic friction acts tangentially to the motion and opposite to the velocity vector but why does static friction act towards...
  47. H

    Newton's force and circular acceleration

    Homework Statement Your niece finds her father's watch. The light watch chain has a length of 35 cm, and the mass of the watch is 190 g. Your niece swings the watch in a vertical circle, maintaining the speed of the watch at 2.4 m/s. Find the tension in the chain when it makes an angle of 43°...
  48. W

    Flatbed truck going round a circular road on an incline

    Homework Statement The problem statement is in the attachments.Homework Equations F=maThe Attempt at a Solution I uploaded the solution to the problem. I have had no trouble deriving the first two equations for the summation of forces in the x, n and t directions, however I am having trouble...
  49. A

    Electromagnetic Rail gun and a circular track

    Two parallel electromagnets situated symmetrically on either side of the straight section of an oval track propel a wheeled trolley along the track, so that the trolley is in continuous motion, as long as the current is supplied to the electromagnets. Is this workable? Does the entry and exit...
  50. T

    Question on circular motion involving astronauts and g force?

    The question is: If an astronaut who can physically withstand acceleration up to 9 times that of free fall (9g) is being rotated in an arm of length 5.0m what is the maximum number of revolutions per second permissible. I approached this by considering 9g to be the centripetal acceleration...
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