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. Pushoam

    B on center of 2 infinite wires with semi - circular end

    Homework Statement Homework EquationsThe Attempt at a SolutionMagnetic field due to both semi - infinite straight wires on P = Magnetic field due to infinite straight wire on P = ## \frac { \mu_0 I } { 2 \pi a } = 2 * 10 ^{-5} ~wb/m^2 ## Magnetic field due to semi – circular wire on...
  2. E

    Circular motion and Kinematics

    Homework Statement l=2m b=1.5m The mass of the chair is 5kg. A boy with a mass of 50kg sits on the chair. The distance of the chair from the pole is 3m, and it spins around it horizontally with a radial velocity of 1.95 rad/s. The boy drops a ball at some moment, what would be its distance...
  3. F

    Cirular Motion - car on a circular ramp

    Homework Statement A 1200 kg car has a speed of 5 m/s at the top of a circular ramp of 10 m in radius. The normal force exerted by the seat of the ramp on the car is : A) 9000N B) 9600 N C)11250 N D)13650 N E)14150 N Homework Equations ∑F=ma ac = m v^2 /r The Attempt at a Solution...
  4. K

    Circular motion, string and ball in a horizontal circle

    A mass m = 0.15 kg is attached to a massless string and rotates at constant speed v = 4 m/s in a horizontal circle of radius 2 m. The tension T (in N) in the string is: (a) 1.1 (b) 1.9 (c) 2.4 (d) 3.3 (e) 4.9 I would assume that first I calculate the centripetal acceleration by using v^2/r =...
  5. A

    Circular Motion - Hanging object swinging around

    Homework Statement An object of mass m is rotating, hanging from a string of known length l. The string is attached to a pole, which rotates with a known angular velocity ω and forms a to-be-determined angle α with the string. Find α. I think I have solved it (the numbers match the results of...
  6. ferrariistheking

    Centripetal Force and circular motion

    Homework Statement Gravity causes a centripetal force that allows satellites to travel around planets. How fast must a 102-kg satellite travel to maintain a circular orbit 352 km above Earth's surface? Homework Equations F=m(v^2/r) -----> (F/m) x r= v^2, then square root F= force m=mass...
  7. parshyaa

    Question about circular motion and acceleration

    In circular motion 1) V = rw and ##\vec V## = r ω##\vec e_{tan}## 2) a = rα and ##\vec a## = -##\frac{v^2}{r}####\vec e_{rad}## + rα##\vec e_{tan}## Where ##\vec e_{tan}## is the unit vector along the tangent in increasing direction of θ And ##\vec e_{rad}## is the unit vector along the radial...
  8. A

    Circular Motion — Object on a rotating conic surface....

    I need help understanding what kind of problem this is at all, since I'm really lost. I'm missing the specific topic name (I called the topic "circular motion" because it's got something to do with it, but maybe it has a more specific sub-topic name), probably missing key formulas, and generally...
  9. Vivek098

    Magnetic Lines of Dipole and Circular Current wire

    What is the difference between the Magnetic Field Lines of the Dipole and Circular Current Carrying Wire at the centre?
  10. F

    I Can angular momentum be applied to non circular rotations?

    One of the reasons I've been so stumped about learning about angular momentum in QM, is that in my classical physics class we only applied it to circular motions. Hence, while I am aware that angular momentum is connected to spherical harmonics, the orbital shapes (besides s) isn't really...
  11. O

    Understanding Circular Motion: The Role of Centripetal Acceleration

    <Moderator's note: Removed template prior to moving it from Homework.> I am looking at centripetal acceleration, and I know that even at a constant speed the object is acceleration because its velocity is changing. But I don't understand how it is changing, like when is it negative and when is...
  12. L

    Centripetal Force / circular motion question

    Homework Statement I'm not asking for a full on solution to my question, but instead wanted to know what was the difference in these two questions. So, here are the two questions 1) A space station of radius 90 m is rotating to simulate a gravitational field. What is the period of the space...
  13. M

    Maximum Speed for Circular Turns: Radius Doubling Question Explained

    Homework Statement The maximum speed with which a car can take a circular turn of radius R is v. The maximum speed with which the same car, under the same conditions, can take a circular turn of radius 2R is A. 2v B. v√2 C. 4v D. 2v√2 Homework Equations v = (2πr)/T The Attempt at a Solution...
  14. L

    Can Tension in Circular Motion Be Equal for Both Ropes?

    Homework Statement Homework Equations F = mv^2/R The Attempt at a Solution I got that T1max = T2max because when i plugged into my formula for centripetal force, i get that both ropes end up with mv^2/R which means they are equal everywhere... Is this correct?
  15. J

    Uniform Circular Motion of Roller Coaster

    Homework Statement Assume the roller coaster cart rolls along the curved track from point A to point C under the influence of gravity. Assume the friction between the cart and track is negligible. What would be the direction of the carts acceleration at point A? (The question in the image does...
  16. L

    Predicting the behaviour of a closed circular airfoil

    I was out and about today and observed a dog walker playing frisbee with their dog. I noticed the frisbee gliding gracefully through the air as the dog jumped to grab it, clutching the ring-like disc in its mouth. It got me to thinking about airflow over the disc, the lift and drag properties...
  17. L

    Tension and Centripetal Force in Circular Motion

    Homework Statement Where does T2cos(theta) come from ? Isn't mv^2/R the centripetal force which is the tension of rope 2? Homework Equations Fc = mv^2/R 3. Solution Wait! The horizontal component of the circle is the centripetal force? So that part is mv^2/R? I got confused and thought...
  18. J

    Acceleration and Gravity with Circular Motion

    Homework Statement You hold a small ice cube near the top edge of a hemispherical bowl of radius 100 mm. You release the cube from rest. What is the magnitude of its acceleration at the instant it reaches the bottom of the bowl? Ignore friction. Homework Equations ΣF = ma Fg = mg The Attempt...
  19. M

    MHB Is the list a circular shift of the other?

    Hey! :o I want to write a progarmm in python that reads two lists A, B and checks if the one of the lists is a circular shift of the other list. The result is either True or False. I thought to do something like that: if sorted(A) == sorted(B): C = True else: C = False But it cannot...
  20. M

    Flux induced in a circular loop

    Homework Statement I have a circular loop with a radius of 1 m. The center of the loop is located 2 m away from a infinitely long current carrying wire, with ac current I. Find the flux in the circular loop Homework Equations Φ = ∫ B ds The Attempt at a Solution I've found a lot of examples...
  21. L

    Work In Circular Motion With Tension

    Homework Statement The speed of the pendulum bob remains constant as it travels around the circle (a) Over one complete circle, how much work does the tension force F do on the bob? (i) A positive amount; (ii) a negative amount; (iii) zero. (b) Over one complete circle, how much work does...
  22. J

    Dynamics and Circular Motion Problem

    Homework Statement A 2 kg tetherball swings around a vertical pole attached to two ropes each at a 30 degree angle from vertical. Each supporting rope is 1.5 meters long, and the ball travels at 8 m/s long. Homework Equations The question doesn't ask what they're looking for, so I assume they...
  23. A

    Force at the Bottom of a Circular Amusement Park Ride

    Homework Statement In an amusement park ride called The Roundup, passengers stand inside a 17.0 m -diameter rotating ring. After the ring has acquired sufficient speed, it tilts into a vertical plane. a. Suppose the ring rotates once every 4.50 s . If a rider's mass is 59.0 kg , with how much...
  24. A

    Is Angular Momentum Conserved During the Changing of the String Length?

    Homework Statement An object with mass m is attached to a string with initial length R, and moves on a frictionless table in a circular orbit with center C as shown in the figure. The string is also attached to the center, but its length is adjustable during the motion. The object initially...
  25. A

    Uniform Circular Motion - distance

    Homework Statement An object with mass m = 2 kg is moving in a uniform circular motion with radius r = 2m as shown in the figure. It takes π seconds for the object to travel from θ =0 to θ = 180 degrees. What is the distance traveled by the object in 20 s...
  26. A

    Solving for Constant Centripetal Acceleration: Understanding Spiral Motion

    Assume an object accelerating at a certain value dV/dt. If this object was traveling in a circular motion the centripetal force would increase as the object moves faster. To maintain centripetal acceleration constant while the object is accelerating (in its forward motion dV/dt) I think it...
  27. J

    Circular motion comparisons question

    Homework Statement A bus of weight Fg is moving at a constant speed over a hill and then over a dip that has the same radius of curvature, when the bus passes over the crest of the hill, the road exerts a normal force on the bus equal to 3/4 Fg. What is the normal force the road exerts on the...
  28. G

    Tension in circular motion with connected masses

    1. The problem statement, all variables, and given/known data A block of mass m1 = 2.00kg is attached to a rope of length L1 = 0.50m, which is fixed at one end to a table. The mass moves in a horizontal circle supported by a frictionless table. A second block of mass m2 = 1.25kg is attached to...
  29. Poetria

    Circular motion - velocity vector

    Homework Statement Which of the following correctly describes the velocity vector in each case? 2. The attempt at a solution I got it wrong at first. My new attempt (I have a sneaking suspicion that I am missing something important): For the first picture: dtheta_1/dt<0 - the angle is...
  30. Peter Coe

    Change in momentum for a satellite in circular orbit

    Homework Statement A satellite is in a circular orbit passing over the North and South geographical poles as it orbits the Earth. It has a mass of 2200kg and its orbit height is 870km above the Earth's surface. What is the change in momentum of the satellite from when it passes over the...
  31. S

    Is Vertical Circular Motion Ever Uniform?

    Hi, I'm quite confused about vertical circular motion (particularly at minimum speed) and would appreciate any help. I'm confused about velocity in a "loop the loop" situation. Say (theoretically) a car was going minimum speed around a loop (which I understand is sqrt of rg). Therefore the total...
  32. S

    Circular Motion question, why does Fnet = 0 (so that T=W)?

    Homework Statement A 0.50kg puck rests on a level air table and is connected by a light thread passing through a hole in the table to support a hanging mass of 3.0 kg. A stable orbit is achieved when the puck is sent into a circular path of radius 0.15 metres around the hole. (A) neglecting...
  33. C

    Question Regarding Circular Motion and Normal Forces

    Homework Statement A roller coaster car has a mass of 500 kg when fully loaded with passengers. The path of the coaster from its initial point involves only up and down motion with no motion to the left or right. (A) If the vehicle has a speed of 20 m/s at the bottom of the first dip which...
  34. P

    Need help with a circular motion question

    Homework Statement A stone has a mass0.2 kg is whirled around on the end of a string of length 20cm. The string will break when the tension exceeds 6kg.m.s-². calculate the maximum speed at which the stone can be whirled around before the string breaks [/B]Homework Equations ? The Attempt at a...
  35. C

    Mechanical energy of a block sliding on a circular path

    Homework Statement ( The following problem is taken from kleppner's " Introduction to mechanics" ) ( The question in the book talks about the velocity but my confusion is related to the Energy ) Homework Equations Conservation of Mechanical energy : Ef - Ei = 0 Consevation of Momentum : Pf -...
  36. T

    Faraday's law -- circular loop with a triangle

    Homework Statement A circular coil with radius a is connected with an equilateral triangle on the inside as shown in the figure below. The resistance for each section of the wire is labeled. A uniform magnetic field B(t) is pointing into the paper, perpendicular to the plane of the coil. B(t)...
  37. J

    Circular Motion and the Law of Gravitation -- question

    Homework Statement Matt Damon is stuck on Mars. He needs to get o the planet and into orbit to rendezvous with the rescue team, which will be orbiting the planet at the same radius as Phobos, one of Mars’s moons. His goal is to determine what his take-of speed should be so that he makes it into...
  38. L

    Surface area of a circular cylinder cut by a slanted plane

    Homework Statement Cylinder : x^2 + y^2 = 1 Plane that intersects above cylinder: y + z = 2 What is the surface area of the sides of this cylinder? Homework Equations dS= R1 d@ dz @ is from 0 to 2 pi z is from 0 to 2 - y dS=(Zx^2 + Zy^2 + 1)^.5 dA Where Z = 2 - yThe Attempt at a Solution I...
  39. A

    Non uniform circular motion acceleration

    In uniform curved motion , I can get the acceleration from the equation : A = v2/r , but in non uniform the velocity is changing , so will the certipetal acceleration also change ?
  40. Adrian555

    Natural basis and dual basis of a circular paraboloid

    Hi everyone!I'm trying to obtain the natural and dual basis of a circular paraboloid parametrized by: $$x = \sqrt U cos(V)$$ $$y = \sqrt U sen(V)$$ $$z = U$$ with the inverse relationship: $$V = \arctan \frac{y}{x}$$ $$U = z$$ The natural basis is: $$e_U = \frac{\partial \overrightarrow{r}}...
  41. A

    Calculating speed in circular motion

    1. Homework Statement A whirlygig is made by hanging a mass, m1 = 386.0 g, through a tube and then spinning another mass, m2 = 198.0 g around so that it forms a circle. When this happens the string makes a small angle with the horizontal as shown in the diagram. If this is done at a specific...
  42. A

    Calculating Tension in Circular Motion

    Homework Statement A whirlygig is made by hanging a mass, m1 = 324.0 g, through a tube and then spinning another mass, m2 = 111.0 g around so that it forms a circle. When this happens the string makes a small angle with the horizontal as shown in the diagram. If this is done at a specific speed...
  43. A

    Circular Motion of bicycle wheel

    Homework Statement A bicycle wheel has a radius of 0.5 m. When it spins, it completes one full turn in 1.6 s. Two identical rocks are stuck on the wheel at a radius of 0.4 m and 0.2 m. What is the ratio of the force on the outer rock to that of the inner rock? Homework Equations F=ma F=mw^2r F=...
  44. S

    Circular Motion: Why an Object Moves When Acceleration is Perpendicular

    Why an object will move in circular when the acceleration is perpendicular to the velocity?
  45. B

    Mechanical Energy of a Homogeneous Circular Wheel Rolling at Different Speeds

    <Moderator's note: Moved from a technical forum and therefore no template.> Hello, first I'm sorry for my English. I have a problem with my exam task, this answer wasn't done good according to the professor and I have not idea how I can do it in a different way.Write mechanical energy...
  46. S

    What Is the Minimum Speed and Tension in a Swinging String with Keys?

    Homework Statement Question: Keys combined with a combined mass of 0.100 kg are attached to a 0.25 m long string swung in the vertical plane. a) What is the slowest speed that the keys can swing and still maintain a circular path? b) What is the tension in the string at the bottom of a the...
  47. K

    Dynamics of a point mass in circular motion

    Homework Statement Dear All, I'm having a hard time solving the following problem: A point of mass is moving on a circular plane (Oxy), where the circle's formula is: The force acting on mass "m" is defined as: We're looking for velocity of point "m" in position (1,1) =V1, and in position...
  48. N

    Small sphere in a circular surface

    Homework Statement A small sphere of radius R held against the inner surface of a smooth spherical shell of radius 6R as shown in figure. The masses of the shell and small sphere are 4m and m respectively. This arrangement is placed on a smooth horizontal table. The small sphere is now...
  49. M

    Uniform Circular Motion Inside a Sphere of Charge

    Homework Statement "*Question 44: Uniform Circular Motion Inside Sphere of Charge The tau particle is a negatively charged particle similar to the electron, but of much larger mass - its mass is 3.18 x 10-27 kg, about 3480 times the mass of the electron and about twice the mass of a proton or...
  50. L

    I Can a Circular Function with Complex Variable Represent a 3D Graph?

    Does a circular function with complex variable represent a three-dimensional graph? For example cosiz
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