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. H

    Accelerating a satellite in a circular orbit

    Hello, I will be thankful if you could explain what appears to me as a paradox. We know that a satellite on a circular orbit, let say around the earth, has a uniform speed given by v=√(GM/r0). Now I would like to accelerate the satellite by keeping it on the same circular orbit r0. The only...
  2. peroAlex

    Induced Voltage of Rotating Circular Loop

    HI! I'm a student, this question appeared in one of the old tests. I though I had it solved but apparently I must have missed somewhere. Could someone please at least hint me where I went wrong? Homework Statement Thin wire is wound into circular frame with radius ## r = 0.05m ## which...
  3. Pushoam

    Tension in a chain with circular motion

    Homework Statement Homework EquationsThe Attempt at a Solution What I know is tension is same in magnitude at all points of the chain along tangential direction due to the symmetry of the system. But how to find it out?[/B]
  4. J

    Circular Motion - Newton's Laws in different reference frames

    Homework Statement A child stands near the middle of a roundabout that is rotating with some angular velocity w. The child moves towards the edge of the roundabout in a straight line from the child's perspective and at constant speed. Explain in as much detail as you can (and using equations)...
  5. G

    Uniform circular motion -- How can radial acceleration have a calculated value?

    In uniform circular motion, direction of particle is changing at every moment but its speed remains the same. If the magnitude of velocity or speed remains the same, change in magnitude of velocity is zero. Then how come radial acceleration can have a calculated value since acceleration = change...
  6. maltmana

    I Planetary Orbits: Force needed for circular orbit

    Hi! first time poster here. I'm making an orbital simulation and I am having a problem with one minor detail. The gravity is working great, and I've programmed it using this formula: A force vector is applied = DirectionOfCentralBodyNormalized * ((GravConstant * centralbodymass *...
  7. Victoria_235

    Circular wire with ball and spring problem

    Homework Statement Here is the problem. A small ball of mass m moves without friction attached to a cwire. The ball moves under the action of gravity and a spring of constant k whose other end is fixed in the point A, with OA = R / 2. The spring is tension free when the spring is R/2 to...
  8. Salvador_

    Tension in a string in circular motion

    Homework Statement A string prq which is fixed at p and where q is vertically below p. r is a smooth ring threaded on the string which is made to rotate at an angular velocity ω rad/s in a horizontal circle centre q, the string being taut. If |pq| = 0.12 m, |pr| + |rq| = 0.18 m, show that...
  9. D

    Find the radius of a particle's circular path

    Homework Statement A particle moves along a circular path over a horizontal xy plane at a constant speed. At time t1= 3.00s, its acceleration vector is given by (3i-5j) m/s^2. At time t2=7.00 s, its acceleration is given by (-3i+5j) m/s^2. Find the radius of the particle's circular path...
  10. O

    Reaction force be 0 at top of circular path swing?

    Homework Statement Hi, I have a question about a bucket filled with water being swung in a vertical circular path. I'm wondering why at the top of this swing, the reaction force of the bucket on the water can be 0? (ie. why is the minimum centripetal force required only the weight of the...
  11. DevonZA

    How Do You Calculate the Inside Diameter and Mass Savings for Hollow Shafts?

    Homework Statement A solid and hollow shaft of the same material must transmit the same maximum torque. The diameter of the solid shaft is 203mm and the outside diameter of the hollow shaft is to be 216mm. a) Determine the inside diameter of the hollow shaft. (answer = 138.7mm) b) What...
  12. Wrichik Basu

    A problem in Inverse Circular Functions in Trigonometry

    Homework Statement :[/B] Solve for ##x ##: $$ \sin ^{-1} {x} +\sin ^{-1} {(1-x)} =\cos ^{-1} {x} $$ Answer given: ##0## or ##\frac {1}{2}##. Homework Equations :[/B] All relevant formulae on inverse circular functions may be used. The Attempt at a Solution :[/B] Please see the pic below...
  13. M

    I Modal frequencies of a vibrating circular membrane? (DRUM)

    I am in the process of trying to develop a modal drum synth. I have the following graphics as references for the frequencies of some of the first modes relative to the fundamental: This is a good start. But I want to be able to model more modes than just that. What is the formula required...
  14. M

    B The definition of a straight-line seems circular?

    Hi,I was just wondering if someone could provide clarity on this matter: that if a straight-line is initially defined as "a shape that forms the shortest distance between two points" and conceptualising that shape [that forms the shortest distance between two points] as one that, at an...
  15. M

    Inclined plane in a circular motion

    Homework Statement u=60km/hr m=1400kg Friction of road (wet road)=0.4 angle of depression=3.65 degrees radius of circle=156.3m Distance of total circumference=983m Distance of circumference needed to go=154m Therefore it must go 56.4/360 degrees to go that distance. [/B] My problem is to find...
  16. Aslet

    A spring-mass system in circular motion

    Homework Statement I uploaded the image of the system to have a visual example. : ) A point mass ## m ## connected to a spring is bounded to move on a circular guide with radius ## R ## without friction. The guide is fixed to a vertical plane and the other extremity of the spring is attached at...
  17. No1_129848

    Uniform Circular Motion, Acceleration problem

    Homework Statement A cat rides a merry-go-round turning with uniform circular motion. At time t1 = 2.00 s, the cat’s velocity is V1 = (3.00 m/s)i + (4.00 m/s)j , measured on a horizontal xy coordinate system. At t2 = 5.00 s, the cat’s velocity is V2 = (3.00 m/s)i + (4.00 m/s)j. What are (a) the...
  18. H

    Frictional Force in Circular Motion: Exploring the Relationship with Radius

    Homework Statement A car drives along a curved track. The frictional force exerted by the track on the car is: a. greater than the frictional force exerted by the car on the track b. directed radially outward c. opposite in direction to the frictional force exerted by the car on the track d...
  19. StudentOfScience

    Displacement Function of an Idealized Circular Loop Coaster

    Homework Statement Suppose we have a roller coaster cart of mass m, which may be approximated as a point mass for our purposes. Ignoring friction and air-drag, what is the displacement of the cart as a function of time? It enters the loop with an initial velocity $$ v_0 \hat i $$ and the radius...
  20. E

    Understanding free-body diagram: Circular Hoop

    Homework Statement Understanding the free-body diagram of a bead on a circular hoop. I am calculating all forces on with x and y direction and a little confused. Why is sin*angle_x and cos*angle_y reverted in this? Usually i go sin with y and x with cos. Why is the force n=mg/(cos*beta) and...
  21. D

    Vertical circular motion with a changing radius

    Hello, I am curious to see how the mathematical analysis of a vertical circular motion with a sensible rope, that is to say, a rope that streches easily, looks like. k- constant of the rope. thanks,
  22. T

    Analyzing Forces in Circular Motion: Ramp and Ball System

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  23. Bunny-chan

    Direction of vector acceleration in circular motion

    There is a problem in my Physics textbook which says: Homework Statement "A car runs counter-clockwise in a circular lane of 1 km of diameter, going through the south extreme at 60 km/h on the instant t = 0. From that point onwards, the driver accelerates the car uniformely, reaching 240 km/h...
  24. D

    Magnitude of force of a disk on a circular track

    Homework Statement A small disc, radius r and mass m = 7.9 g, rolls on its edge. The friction with the track is enough to prevent slipping. When released, it rolls down the track (sketch) and reaches a circular section with radius R = 5.1 cm, which is very much greater than r. The initial...
  25. physicaled

    Circular Motion: Ball on String

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  26. C

    Circular polarization in rectangular waveguide

    Homework Statement In a rectangular waveguide, b = a/2, find the section, if exists, in which the magnetic field is circularly polarized (TE10 mode). Homework Equations Rectangular waveguide equations for TE10 mode (referencing Pozar book). Circular polarization (π/2 out of phase and same...
  27. Cathr

    Circular motion of an electron in a magnetic field

    Imagine we take a vertical, infinite wire and we let electric current pass through. The charges create magnetic field all around the wire. Now if we introduce an electron in the magnetic field, it will have a circular motion around the wire. The Lorentz force is not conservative, this means...
  28. cheapstrike

    Tension in a flexible circular loop

    Homework Statement A small circular flexible loop of wire of radius R carries a current I. It is placed in a uniform magnetic field B. The tension in the loop will be double if A) I is doubled B) B is halved C) r is doubled D) both B and I are doubled. Homework Equations The Attempt at a...
  29. V

    Point of Maximal Tension for Vertical Circular Motion

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  30. B

    Question about Magnetic induction of circular loop

    Homework Statement Homework EquationsThe Attempt at a Solution This is what i did about (a) but i don't know how to approach (b), it doesn't have x,y components, only Bz component.
  31. I

    Bending stiffness of circular bars

    Which of the two is stiffer in bending? 1. A circular rod of diameter D and length L. 2. A circular rod of diameter d and length L, surrounded by a tube of inner diameter d, outer diameter D, and length L. The tube is not bonded and can freely move. It seems like an easy solution in that we...
  32. D

    What forces are acting on the rotating mass and platform in this experiment?

    Homework Statement The pre-lab is based on the following lab: http://iws.collin.edu/mbrooks/physics/experiments/PHYS 2425 Exp 7 Manual.pdf Moderator edit: Extract of an image from the PDF showing the mechanism under discussion: 1. Draw two free-body diagrams for the rotating mass in teh...
  33. Khunpol Jermsiri

    Circular motion object falling in the circle

    Homework Statement An object with mass of m traveling in a circle rail ,when reached point A the object derailed and moved in a parabola path to point B and so on find the length of AB in term of R and theta. given that B is on the same horizontal level as A Homework EquationsThe...
  34. Vitani11

    Does ω0 = ωf when radius of circular motion changes?

    Homework Statement A particle of mass m is moving on a frictionless horizontal table and is attached to a massless string that passes through a tiny hole of negligible radius in the table, and I am holding the other end of the string underneath the table. Initially the particle is moving in a...
  35. G

    I Circular electron propagation in carbon nanotubes?

    Can carbon nanotubes support electron propagation perpendicular to the axis? That is, can there be circular current flow on the tube's perimeter, not just the linear flow parallel to the axis? Because I reading that it's generally considered a 1-dimensional conductor.
  36. B

    Tangential and centripetal acceleration in circular motion

    I'm trying to understand the geometrical meaning of acceleration in circular motion. When I consider a particle moving in a circular path, I can clearly see that the acceleration vector can be composed of a tangential and radial component. But since the change in velocity happens over a period...
  37. Rodriesk

    Magnitudes and Directions In Uniform Circular Motion

    Homework Statement A biker is 40.0m to the east of a flag in a park, heading south at 10m/s. 30.0 seconds later, the biker is 40.0m north of the flag and heading east at 10.0m/s. For the biker in this 30.0s interval, what are: a) the magnitude and direction of the displacement? b) the magnitude...
  38. rumborak

    A circular current-carrying wire floats in space....

    Maybe there's a tiny battery somewhere, just to make it realistic. The wire is also very thin, and thus needs little to no force to be bent. What happens to the wire? Does it twist on itself because each piece of the wire experiences a Lorentz force due to the magnetic field of the wire on the...
  39. grandpa2390

    Electric field due to a flat circular disk

    Homework Statement Find the electric field at a distance z above the center of a flat circular disk of radius R Homework EquationsThe Attempt at a Solution My attempt to solve this was take the line integral from the center of the circle to the edge. Then, knowing the circle is symmetrical...
  40. J

    I Why is the area of a circular cap on a sphere not equal to πr^2?

    I had a question regarding calculating the area of a circular cap on a sphere. From what I’ve read, the area should be calculated according to; $$A = 2πr^2 \cdot (1 – cos (\frac{θ}{2} )$$ However, I have another way but I don’t understand why this isn’t correct. The circular area can be...
  41. Q

    Calculating P for an Aircraft Flying in a Circular Motion

    Homework Statement An aircraft flies with its wings tilted, in order to fly in a horizontal circle of radius r. The aircraft has mass 4.00 x 104 Kg and has a constant speed of 250ms-1 . with the aircraft flying in this way, two forces are acting on the plane, P [lift] and W [weight which is...
  42. Edward Barrow

    I Will an elliptical orbit self-correct into a circular one?

    I know that moons tend to orbit their planets in a slightly elliptical orbit rather than a perfectly circular orbit. But for the purpose of this thread, let's assume that moons effectively orbit their planet in a circular orbit. So here is the question... If our moon was struck by an object...
  43. J

    With a circular orbit, when do I use 1/2mv^2

    Homework Statement At a circular orbit and at an elliptical orbit when do I use 1/2mv^2 instead of the kinetic equation from which I derived from F=GMm/r^2 which is Ek = GMm/2r Homework Equations F=GMm/r^2, Ek = GMm/2r, Ek = 1/2mv^2 The Attempt at a Solution For instance, when I tried to...
  44. F

    Circular motion: ring on string

    Homework Statement Homework Equations F = mw^2r [/B]The Attempt at a Solution For part a, I can't get the constant of half with the tan a I am getting tan a = w^2l/g
  45. F

    Understanding Circular Motion in a Cone: Solving for Radius and Normal Force

    Hello I am a little confused by the following problem: Mass in cone: A particle of mass m slides without friction on the inside of a cone. The axis of the cone is vertical, and gravity is directed downward. The apex half-angle of the cone is θ, as shown. The path of the particle happens to be a...
  46. F

    Triangular shaft change to circular shaft

    Homework Statement for the circular cross section shaft , why we need to put an sin60 as to get the area ? Homework EquationsThe Attempt at a Solution why the area shouldn't be pi(0.004) ^2 only ?
  47. J

    Inertia (and, to some extent, circular motion again)

    I often hear inertia used as an explanation in areas where it seems to make intuitive sense, but appears to me to be inconsistent with the definition of inertia as just depending on an object's mass. I offer three examples (they're very similar): Example 1: An elevator Suppose an elevator...
  48. Clara Chung

    Question about circular motion on a horizontal road

    Homework Statement Homework EquationsThe Attempt at a Solution Why can't we take the moment on the left wheel? In this case, 2d(N2) - mgd = mgd + m(v^2)h/r - mgd =m(v^2)h/r ≠ 0 Shouldn't there be an anticlockwise moment about the left wheel?
  49. Kernul

    What Forces Act on a Train Engine Going Around a Circular Curve?

    Homework Statement A train engine of mass ##m## is chugging its way around a circular curve of radius ##R## at a constant speed ##v##. Draw a free body/force diagram for the train engine showing all of the forces acting on it. Evaluate the total vector force acting on the engine as a function...
  50. Const@ntine

    Aeroplane follows circular trajectory-Tension? (geometry)

    Homework Statement So, I have this problem here that's pretty basic, but the solution manual sets different axes, and I'm having a bit of trouble understanding the geometry part, meaning how he applies the given forces to the new axes. A model airplane of mass 0.750 kg fl ies with a speed...
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