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. Hardikph

    Is Δθ in a circle equal to the angle in a velocity vectors triangle?

    How is Δθ in circle equals to angle in velocity vectors triangle? I tried using simple geometry but I can't.
  2. C

    Circular + Projectile Motion question

    Homework Statement A ball was placed in a frictionless circular track with radius R and given initial velocity of u.The ball went around the cricle ,left at some point,then arrived in the same initial position after undergoing projectile motion. a.State the speed u in terms of R and g...
  3. J

    I Decomposing the arc length of a circular arc segment

    A particle travels along a circular arc segment centered at the origin of the Cartesian plane with radius R, a start angle θ1 and an end angle θ2 (with θ2 ≥ θ1 and Δθ = θ2 - θ2 ≤ 2π). The total distance traveled is equal to the arc length of the segment: L = R(Δθ). I would like to find the...
  4. J

    Circular loop in magnetic field

    Homework Statement A circular single loop of wire with a diameter of 20.0 cm lies in the plane of the paper in a region of space that contains a 1.75 T magnetic field pointing out of the paper. a) Determine the magnetic flux through this loop. b) If the diameter of the loop changes from 20.0...
  5. CentrifugalKing

    Circular Wave Fronts Emitted by Two Wave Sources

    Homework Statement https://session.masteringphysics.com/problemAsset/1383558/3/21.EX26.jpg Make a table with rows labeled P, Q, and R and columns labeled r1, r2, Δr, and C/D. Fill in the table for points P, Q, and R, giving the distances as multiples of λ and indicating, with a C or a D...
  6. Runei

    I Some weird circular relationship

    Hello there! I'm currently doing some mathematical modelling at my work, and I have arrived at an interesting kind of circular relationship integral - and now I'm wondering about what to do. The integral looks very innocent at first glance: $$ \theta_s = \int\limits_0^{t_1} \omega (t) dt$$ So...
  7. F

    Understanding Circular Motion: The Relationship Between Force and Velocity

    If a force acts on an object perpendicular to its velocity, why does the speed remains unchanged? Wouldn't the force give rise to a vertical component of velocity on the object and thus increase the speed of the object?
  8. R

    Finding Mass Center of a Circular Disc with Hole & Weight

    Why do we take the Center of mass to be on the right side rather than on the left? A uniform circular disc of radius 4a with a circular hole of radius 2a made in the disc. The mass of L is m and a particle of mass km is now fixed to L at the point P. The system is now suspended from the point S...
  9. H

    I Prove slant surface of a cone is always a circular sector

    In the elementary proof of the slant surface area of a cone ##A=\pi r s##, where ##s## is the slant height, it is assumed that the net of a cone is a circular sector. In other words, if we cut the slant surface of a cone from its apex to its base along a straight line, the resulting surface can...
  10. V

    Why are eddy currents circular?

    i tried to fig it out by watching a lot of vid on it but no chance help me
  11. R

    Gravitational force - point mass and circular platform

    Homework Statement Calculate the gravitational force between a point mass and a circular platform. Homework Equations G=m1*m2/r^2 The Attempt at a Solution http://i.imgur.com/dfZf9GK.jpg The actual solution is different. They integrated by the angle between a/r (alpha) but i do not...
  12. S

    Questions about understanding circular motion & the forces involved

    Hey, I'm having some difficulty in understanding circular motion and it's forces. Here is the situation I'm on: Imagine you are on a smooth turn-table with smooth shoes and the table starts spinning. Because of inertia, and because the frictional force is not nearly enough to keep you going in a...
  13. E

    A Can we make a circular polarization laser directly?

    Now,we get the circular polarization photon using 1/4 waveplate, can we make a circular polarization laser directly through Stimulated Emission Radiation? or, when a electron transition from one level to another level,what kind of polarization of the photon, linear or circular? thank you!
  14. Part Toon

    How do you magnetize a circular magnet?

    < Mentor Note -- thread moved from New Member Introduction Forum > Hello, this is actually my first post on Physics Forums (I just joined) The question above is the one that I thought that would grab the most attention. I actually have 3 questions concerning magnets... I require a special...
  15. W

    Required conditions for vertical circular motion to occur?

    For the case of a particle attached to an inextensible string which is hanging at rest and then provided an impulse horizontally, what conditions must the system meet in order to allow for COMPLETE circular motion. I am well aware the tension at the apex of the motion must be satisfy one of the...
  16. Biker

    Magnetic fields in circular loop

    If I have a some a wire and I took part of it and created a circle. If I want to calculate the strength of the magnetic field at the center of it. I should just use the magnetic field equation for the circular loop, shouldn't I? ## B = \frac{U_o N I}{2R} ## and I shouldn't care about the...
  17. N

    How Do You Calculate Acceleration in a Limacon-Shaped Path?

    Homework Statement The rod OA rotates clockwise with a constant angular velocity of 6 rad/s. Two pin-connected slider blocks located at B move freely on OA and the curved rod whose shape is a limacon described by the equation r = 200*(2-cosθ) mm. Determine the magnitude of the acceleration of...
  18. N

    Circular motion -- Car on a circular track

    Homework Statement A car has an initial speed v0= 20m/s. It increases its speed along the circular track at s=0, at=(0.9s) m/(s2), where s is in meters. Determine the time needed for the car to travel 35m. The radius of curvature of the track is 40m. Homework Equations an = v^2/p a = dv/dtThe...
  19. E

    Can a Stone Remain in Circular Motion if Tension Equals Zero Before Velocity?

    Let's say I have a stone tied to a string and I'm spinning it vertically. Now, if I provide an initial velocity such that the velocity of the stone = 0 at an angle greater than 0 from the horizontal(visualize it in the "first quadrant") the eq of motion would be: T+mgsin (theta) = mv^2/r. If the...
  20. M

    Modeling 2D vs. 3D Flow in a Circular Pipe

    Hi everyone! I have the following problem. I have a two phase flow in a circular pipe and I want to model it. I need to decide and justify whether the model should be 2D or 3D. For the moment, I can say only one thing: considering z-axis in the length direction (that it is the dominant one) I...
  21. diazdaiz

    Kinematics and dynamic circular motion of conical pendulum

    Homework Statement [/B] find the period with only using L (for the long of the rope), R (for the radius), M (for the mass), and G (for the gravity) Homework Equations V=ωR Fcentripetal = ##\frac {MV^2} {R}## Fgravity = MG phytagoras basic trigonometry The Attempt at a Solution [/B] i have...
  22. physea

    Normal reaction in banked road circular motion

    Homework Statement Homework Equations ΣF=0 The Attempt at a Solution Basically I don't agree with this solution, I think it is R1 + R2 - mgcos5 + mv^2sin5/r = 0. Can you help me please? thanks!
  23. physea

    Normal reaction in banked road circular motion problem

    What is the equation of forces please for the axis parallel to the banked road? Is it R1+R2-mgcosθ=mV^2/r or R1+R2-mgcosθ=-mV^2/r? Can you advise me please?
  24. RoboNerd

    Question kinetic energy in circular motion

    Homework Statement An object moves in uniform circular motion. Its kinetic energy is directly proportional to: I. centripetal force II. radius of the circle III. the period of circular motion Homework Equations I took the universal gravitational law G* m1 * m2 /r^2 = m2 * v^2/r and then I...
  25. S

    Magnetic field strength for circular loop

    When deriving the magnetic field strength due to a circular loop at some distance away from it's center (using Biot-Savart's law), why is the angle between ds and r 90 degrees? This is a youtube video with the derivation, see 5:55
  26. B

    Approximating Differential Equations with Taylor Series

    Having trouble with the following problem: A small particle slides along the bottom of a 10 inch radius circular bowl. Neglect friction and assume small oscillations. If the particle has a speed of 15 in/s when it is at the bottom of the bowl, determine a. The differential equation governing...
  27. Carter Green

    I Degredation of a Circular Flow

    Hi I am trying to understand what forces are at work to slow a liquid flowing in a circular pipe As an example the above torus pipe fully filled with an incompressible low viscosity liquid. This is rotated until the fluid achieves solid body rotation and then the pipe is suddenly stopped...
  28. U

    Counting Question Concerning Circular Arrangements

    Homework Statement I have two questions. I'm not sure if I'm allowed to post two at once so I'll start with one "Twenty boys and twenty girls are to take a ride on a Ferris wheel with twenty pods. How many ways can they be arranged if each pod is to contain one boy and boy girl" Homework...
  29. K

    Volume of Right Circular Cone: How to Calculate Using Integration

    Homework Statement Find the volume of a right circular cone with height h and base radius r. Homework EquationsThe Attempt at a Solution I've chosen the case where y = x = r = h. Then, I solve the integral in the image above and I got the book's answer. But is it actually correct?
  30. UMath1

    Why is the speed of orbiting satellites constant?

    As I understand it, satellites orbiting the Darth are constantly falling but keep missing. Why then is their speed constant? Why do they not tangentially accelerate like spaceships do when using a gravity assist? I understand that the force of gravity is perpendicular to the satellites motion...
  31. RoboNerd

    Question about circular motion of planets

    Homework Statement Homework Equations I know that Fc = m * centripetal acceleration, where the Fc = the force of gravity The Attempt at a Solution [/B] I was able to use process of elimination to get B for 25 correctly, but I am not able to understand how it is the right answer. How can...
  32. BiGyElLoWhAt

    I Doppler shift for an observer in circular motion

    Say we have an observer in perfectly circular motion around a source, like a star. Is it reasonable to apply the angle change formula ##cos \theta_o = \frac{cos \theta_s - \frac{v}{c}}{1-\frac{v}{c}cos \theta_s}## and then take the component of the motion parallel to the light wave in the...
  33. sushichan

    [Mechanics] Circular motion outside sphere

    Homework Statement A marble rolls from the top of a big sphere. What is the angle θ when the marble is about to leave the sphere? Assume a zero speed at the top. Homework Equations The question came from the chapter Mechanics - circular motion. The Attempt at a Solution I can't conceive what...
  34. Toughnuke

    Electromotive force (EMF) of a circular loop wire

    Hi, so, I got help from this homework problem by posting it on chegg, but I want clarification. A circular loop of wire of radius 12.0 cm is placed in a magnetic field directed perpendicular to the plane of the loop and into the page. The field is decreasing at a constant rate of 0.050 T per...
  35. R

    Satellite in circular orbit with friction

    Homework Statement A satellite with mass 848 kg is in a circular orbit with an orbital speed of 9640 m/s around the earth. What is the new orbital speed after friction from the earth’s upper atmosphere has done -7.50·109 J of work on the satellite? Does the speed increase or decrease? Homework...
  36. 2

    A ball is swung in a circular path

    Homework Statement A 0.5 kg ball is swung in a circular path from a 80 cm long rope, attached to a vertical pole. A. What is the speed of the ball theta (between the pole and rope) is 40 deg? B. What is the KE of the ball at theta = 40 deg? C. The ball slows down and the KE drops to 50% of the...
  37. Oribe Yasuna

    Circular Motion in a Simple Mass Spectrometer

    Homework Statement In the simple mass spectrometer shown in the figure below, positive ions are generated in the ion source. They are released, traveling at very low speed, into the region between two accelerating plates between which there is a potential difference ΔV. In the shaded region...
  38. Abhijeet Verma

    Time Period of Vertical Circular motion

    Since the latex is not appearing, I request you to please click https://brilliant.org/discussions/thread/time-period-of-vertical-circular-motion/ , to view with complete formatting. Please help. Thanks. P.S-This is not schoolwork or homework...
  39. I

    Circular Motion/Newton's Laws-- Swinging a Pail

    Homework Statement You tie a cord to a pail of water, and you swing the pail in a vertical circle of radius 0.700 m What minimum speed must you give the pail at the highest point of the circle if no water is to spill from it? Homework EquationsThe Attempt at a Solution I got the correct answer...
  40. popo

    How Does Rolling Friction Affect a Toy Train's Motion on a Circular Track?

    Hi, thanks for taking a look! A toy train rolls around a horizontal 1.4-m-diameter track. The coefficient of rolling friction is 0.12. (a) What is the magnitude of the train's angular acceleration after it is released? (b) How long does it take the train to stop if it's released with an...
  41. R

    How Is Deflection Calculated for a Partially Supported Circular Lid?

    Hi In one of my application I am using a linear actuator to lift a 30kg lid which has a diameter of 380mm. I can only use 1/3rd portion on the lid to take support, for actuator which I used a 60*20*180 long plate mounted to the lid and lift. How to calculate the deflection of lid when lifted to...
  42. S

    Horizontal circular motion problem, what am doing wrong?

    Homework Statement The County Fair Swing carries the mass of riders and chairs in a circular path in a horizontal plane while suspended by cables or chains. Let's assume that: Each chair with riders is supported by a single cable The tension in the cable equals 2 x the total weight riders...
  43. D

    Simulated circular motion on a roller coaster

    Homework Statement A roller coaster at the Six Flags Great America amusement park in Gurnee, Illinois, incorporates some clever design technology and some basic physics. Each vertical loop, instead of being circular, is shaped like a teardrop. The cars ride on the inside of the loop at the top...
  44. adremja

    EM wave with circular polarization interferes with conductor

    Homework Statement EM wave with circular polarization travels in directon z interferes with perfect conducting surface xy. 1. find reflected wave 2. calculate induced charge density and surface current induced on conducting surface Can you verify if I started point 1. correctly, and give...
  45. Neeps

    Sailboat rudder physics, and water flow estimate

    Hi. I'm a computer science student developing a kalman filter for autonomous sailboat, but I severely lack knowledge of the physics behind sailboats. I have a wind sensor giving data about wind speed and wind velocity, problem is the data is unreliable. So i thought that i could estimate what...
  46. C

    How Does Circular Polarization Arise in String Wave Motion?

    Homework Statement The horizontal component of a wave is in the y-direction, and the vertical component is in the x-direction. If the horizontal and vertical components of a wave on a string have the same amplitude and are 90 degrees out of phase (say δv=0 and δh= 90°). At a fixed point z...
  47. C

    Force Analysis in Circular Pipe: How to Approach Vertical Force Balance?

    "Consider a fully developed laminar flow in a circular pipe, perform force analysis on an element of the real fluid." I've just started this type of question, and I'm a bit confused about where to go from here: I've managed to do a force balance horizontally to show that the partial derivative...
  48. R

    Uniform circular motion - finding velocity

    Homework Statement Homework Equations radial acceleration = v^2/R The Attempt at a Solution I'm unsure if we have to mention the tension of the cable, but I'm guessing L2 will suffice? Correct me if I am wrong. Anyways, I drew the diagram from a side view (kind of like a circular pendulum)...
  49. K

    Circular Motion and Energy Calculations

    Homework Statement A) An object moving along the x-axis is acted upon by a force Fx that varies with position as shown. How much work is done by this force as the object moves from x = 2 m to x = 8 m? B) A 50-kg child riding a Ferris wheel (radius of wheel R = 10 m) travels in a vertical...
  50. P

    Circular motion and acceleration

    If you are twirling a rock around your head with a rope (assuming it is uniform circular motion), then the only acceleration that is acting is radial. So if you take a look at the rock at any given instant, its velocity is perpendicular to its acceleration. My question is, why does the rock not...
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