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. P

    Lost with exercise about circular motion

    Hi everyone, my physics final is coming in 3 days:cry: , and I really need to have an answer to this exercise , but I'm stuck ! I don't even understand the problem statement HELP ! A typical fastball is thrwon at approximately 90 mph and with a spin rate of 113 rpm (I don't understand what it...
  2. B

    Net Force on a circular current carrying wire, from an infinite wire.

    Homework Statement -I've attached a picture of the problem- An infinitely long straight wire of steady current I1 is placed to the left of a circular wire of current I2 and radius a as shown. The center of the circular wire is distance d(≥ a) away from the straight wire. Let’s find the net...
  3. C

    Stability Condition for Circular Orbit

    Homework Statement Show that the stability condition for a circular orbit of radius a, i.e. f(a) + \frac{a}{3} (\frac{df}{dr})_{r=a} < 0 is equivalent to the condition \frac{d^2V(r)}{dr^2} > 0 for r=a where V(r) is the effective potential given by V(r) = U(r) +...
  4. J

    Electron enters uniform magnetic field and takes circular path

    Homework Statement A time t = 0 an electron enters a region of uniform magnetic field B = 0.010 T and has kinetic energy of 6.40E-16 J. It goes through a half-circle, exits the field and then accelerates across a gap with a potential difference of 2000 V, increasing in speed. It then hits a...
  5. ShayanJ

    Metallic cube with circular hole

    There is a cube with its sides equal to d and its thikness equal to t. It also has a circular hole at its center with radius a (a<<d). Two sides of the cube are maintained at potentials V_0 and -V_0 . I want to find the potential inside the cube but I see no way for obtaining the boundary...
  6. S

    How Fast Must Earth Spin for Equatorial Weight to Be One Fifth of Polar Weight?

    Homework Statement What must be the period of rotation of the Earth on its axis so that a person at the equator will have a reading on the scale that is approximately one fifth as much as he would at the North Pole? (Given on the formula sheet) Radius of Earth = 6.37 x 10^6 m Homework...
  7. P

    Finding the tension in a circular pendulum without radius or angle.

    Homework Statement Some kid is playing with a yoyo of mass m. The yoyo string is let out to length L, and is spun in a horizontal circle at a constant rate of ω. The yoyo string makes an angle of θ with the horizontal m = 39 grams = 0.039 kilgrams L = 46cm = 0.46m ω = 3 rads/sec...
  8. A

    Elastic collision, one object in circular motion

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  9. C

    Forces: mass on a string circular motion

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  10. D

    MHB Mechanics-Conical pendulum, circular motion

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  11. A

    Thermal Expansion of a circular steel plate

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  12. Entanglement

    Why is the magnetic field of a wire circular

    The title is enough
  13. E

    Acceleration in Circular Motion

    Could anyone help my with proving that the acceleration of an object that is moving with uniform circular motion is directed towards the centre of the circle and is of magnitude ω^2(r). Thanks
  14. A

    Transition from inertial to circular motion

    Suppose that we have a body that is moving at a straight line, inertially wrt to another frame. If it starts to move in a circular way after that, what can be said about the motions of its points. Do all points have to deccelrate to achieve the circular motion, but in a different manner, since...
  15. K

    A block on a frictionless circular ramp

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  16. KiNGGeexD

    Electrostatic potential of a circular ring

    I'm a little stumped with this problem, I have posted a photograph below as there is a diagram to compliment the questionExpressions which I used where V(r)= k q/r Where q= σ da Where da is an element of area And k= 1/4πεI messed around with these expressions for a while but it didn't really...
  17. LydiaAC

    Approximate inductance of a filamentary circular current loop

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  18. C

    Find area of the region bounded by the circular arc in 1st Quadrant

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  19. binbagsss

    EM , magnetic field at centre of a carrying circular loop

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  20. J

    Dimensioning of hollow square and circular rod

    Hi Can someone tell me how to determine dimensions for a square hollow rod and circular hollow rod when the material and maximum load is known?
  21. L

    Finding the tension of the string (vertical circular motion)

    Homework Statement A ball of mass 125g is attached to a string .900 meters long. It is then set into vertical circular motion with 38 RPM. What is the tension of the string at the top of the circle and at the bottom of the circle? Homework Equations ∑Fy = may = marad arad = v2/R =...
  22. U

    3D Harmonic Oscillator Circular Orbit

    Homework Statement I found this in Binney's text, pg 154 where he described the radial probability density ##P_{(r)} \propto r^2 u_L## Homework Equations The Attempt at a Solution Isn't the radial probability density simply the square of the normalized wavefunction...
  23. A

    Uniform Circular Motion and Centripetal Force

    Hey guys, first post here! Hoping to get a little help. Homework Statement You are a traffic safety engineer in charge of determining safe speeds for roads. A particular banked curve has a radius of 11.0 meters and is banked at an angle of 8.00°. The coefficient of static friction between...
  24. I

    Different Situations Related To Circular Motion

    Hello, I was asked to make experiments related to circular motion. The experiments will engage on different situations related to circular motion that we need to explain such as: -Analyzing the forces and the acceleration of a ball that moving circularly in a squared glass compared to the same...
  25. U

    Orbital Angular Momentum as Generator for Circular Translations

    Homework Statement Taken from Binney's Text, pg 143. Homework Equations The Attempt at a Solution From equation (7.36): we see that ##\delta a## is in the direction of the angle rotated, ##\vec{x}## is the position vector, and ##\vec{n}## is the unit normal to the plane of...
  26. Matejxx1

    Torque with constant circular velocity

    Homework Statement a passenger with height 175cmis driving on a city bus. The center of mass is at h=110cm above the middle point of the shoe which are 30 cm long. The passenger is standing in the direction of the ride. h=175cm h*=110cm shoe size = 30 cm b) the bus is driving in a circle...
  27. P

    Mathematics of circular shifts of rows and columns of a matrix

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  28. P

    How Do You Calculate Sun's Gravitational Acceleration at an Asteroid's Orbit?

    Hi. I am a little stuck and I would appreciate some help. What is the acceleration due to gravity of the sun at the distance of 1.6 X 10^11 m? The asteroid revolves around the sun in 398 Earth days. 2. Homework Equations : F= (m*V^2)/r3. The Attempt at a Solution : First I found the...
  29. J

    Interference of Sound Waves in a Circular Tube

    1. A sound wave with frequency f = 2300Hz is sent into a circular tube of radius R=160cm through an opening at some point A. A receiver lies at point B, separated from A by an angle α=130°. The speed of sound in air is v=330 m/s. Sound propagates from A to B in both directions along the...
  30. D

    Linear and circular accelerators

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  31. N

    Circular motion and energy of a massless spring

    Homework Statement A massless spring of constant k is fixed on the left side of a level track. A block of mass m is pressed against the spring and compresses it a distance d, as shown in the figure. The block (initially at rest) is then released and travels toward a circular...
  32. E

    Mean ray length from apex to base of an oblique circular cone

    Consider an oblique circular cone of altitude h, base radius R, with apex directly above a point on the base circumference. What is the mean length (& variance) for the set of all rays from the apex to points on or within the base circumference?
  33. L

    MHB What Is the Optimal Size of a Cylinder in a Cone to Maximize Volume?

    In a cone circular line of 15 cm in height and radius 5 cm fits a body cylindrical topped by 1 hemisphere tangent to the base of the cone. Calculate the height and radius of Ia part cylindrical if the volume of the registered body is the largest possible Answer R = H = 3 cm V= pir^2h/3 cone...
  34. R

    Insulated boundary for circular laplace equation?

    Homework Statement Consider the Laplace’s equation, ∆u(r,θ) = 0, inside the quarter-circle of radius 2 (0 ≤ θ < π, 0 ≤ r ≤ 2), where the boundary θ is insulated, and u(r,\theta/2)=0 Show that the insulated boundary condition can mathematically be expressed as \frac{\partial u}{\partial...
  35. J

    Simultaneity in circular motion

    Hey guys based on the Einstein train thought experiment we can say that different inertial frames disagree on simultaneity. In that specific example, the train observer is moving towards one thunder, and away from the second and in his frame the thunder in front of him occurs first followed...
  36. R

    Time Dilation Between Fixed Point & Geostationary Orbit: SR & Circular Motion

    Sorry if this has been asked a lot before but I did try a quick search for this but could find a simple answer. If I am at a fixed point on the equator and a friend is in a space station in a geostationary orbit, and ignoring GR, will their be time dilation between us? Or can we be...
  37. D

    Intensity for circular polarised light through linear polariser

    Hi, does the intensity change when circularly polarised light passes through a linear polariser? I am thinking of a flow like this: natural light -> vertical linear polariser -> quarter wave plate -> horizontal linear polariser -> intensity? After the first polariser, the intensity is 50%...
  38. T

    Calculating Flux Through a Circular Ring

    Homework Statement A particle having charge q = 8.85 μC is placed on the axis of a circular ring of radius R = 30 cm. Distance of the particle from centre of the ring is a = 40 cm. Calculate electrical flux passing through the ring. Homework Equations Flux through a surface = ∫E.ds...
  39. Abel Cavaşi

    Is Complex Torsion the Key to Understanding Circular Helices Operations?

    The following definitions are correct? We associate to a circular helix a complex numbers called complex torsion defined as follows: Definition: It's called complex torsion associated to a circular helix the complex number q=\tau+i\kappa , where \tau is the torsion of circular helix...
  40. Ookke

    A stationary photon for an observer in circular motion?

    Let's imagine a rocket orbiting the earth. The rocket could be any real rocket with moderate speed, so that relativistic effects are not significant, and also rocket does not experice notable centrifugal or other acceleration (so the rockets reference frame would appear almost inertial). A...
  41. P

    Uniform circular motion and angular momentum?

    Homework Statement A sphere on top of a table is attached to a rope which goes through a hole in the table and is attached to a bucket at the other end. The sphere moves in a uniform circular motion with radius R. Water is then added to the bucket and the radius for the sphere's circular...
  42. Vigardo

    Inflation of a clamped isotropic and thin circular plastic membrane

    Appreciated experts, I want to model the inflation of a thin and isotropic circular plastic membrane clamped by a ring. I need to determine the maximum deflection at the pole, stresses, strain, etc..., as a function of the applied pressure difference. The large deflection range complicates it...
  43. W

    General Quantization of Motion in Circular Orbits

    For this question, I have to obtain a general quantization of motion in circular orbits by combining the equations (Where U(r) is potential energy): (mv2)/r= |(dU(r))/dr| With the angular momentum quantization of: mvr= nℏ Then use this to calculate the spectrum for circular motion in a...
  44. J

    Circular motion question - finding rpm

    Homework Statement A 0.60 kg sphere rotates around a vertical shaft supported by two strings, as shown. If the tension in the upper string is 18 N. Calculate the tension in the lower string? the rotation rate (in rev/min) of the system? Homework Equations v=2(pi)r/T Fr= mv^2/r ω =...
  45. G

    Centripetal acceleration and circular motion

    My question is about the centripetal acceleration formula |a| = ω^2*r. If we keep the angular speed constant then why does increasing the radius increase the centripetal acceleration? I don't find this intuitive because the velocity vector is being turned by the same amount each second, if ω is...
  46. U

    Electron revolving in a circular path

    Homework Statement An electron is at P at t=0. It is circulating in anti-clockwise direction with a constant angular speed ω along the shown(see attachment) circular path. Magnetic field at Q (CQ=2R, where R is radius of circle) will be recorded as zero at times ....? The Attempt at a...
  47. G

    Circular Motion: Proof for Non-Uniform Circular Motion Acceleration

    I have seen the derivation of the centripetal acceleration formula a=v^2/r by saying r= rcosθi+isinθj=rcosωti+rsinωtj and differentiating twice. Since ω is constant we get a=-ω^{2}r. I've started looking at non-uniform circular motion where there is also the tangential acceleration vector...
  48. L

    MHB 3) Calculate the dimensions of the straight circular cone, smaller volume that can be circumscribed

    3) Calculate the dimensions of the straight circular cone, smaller volume that can be circumscribed around a cylinder of RADIUS "R" and height "H". Answer is h = 3H and r= 3R/2
  49. 99.9% Void

    Solving Circular Thermodynamics: Calculating Heat Flow & Boundary Temperatures

    Hey everybody, no idea if this is the right place for me to post this… This is the first post I've ever written, in any forum, ever. Complete forum newbie with a complex problem, hence my desperate plea for help on this nexus of knowledge forged through experience that I have yet to gain...
  50. N

    Two Circular Motion Questions. Pendulums

    Homework Statement Got my first physics assignment and I've been able to work out (I think) all of them except these two. 1. A conical pendulum has length 1.5m and rotates at 4ms^-1. What is its angle to the vertical? 2. A mass moves in a vertical circle attached to a fixed point by a...
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