Circular motion Definition and 1000 Threads

In physics, circular motion is a movement of an object along the circumference of a circle or rotation along a circular path. It can be uniform, with constant angular rate of rotation and constant speed, or non-uniform with a changing rate of rotation. The rotation around a fixed axis of a three-dimensional body involves circular motion of its parts. The equations of motion describe the movement of the center of mass of a body. In circular motion, the distance between the body and a fixed point on the surface remains the same.
Examples of circular motion include: an artificial satellite orbiting the Earth at a constant height, a ceiling fan's blades rotating around a hub, a stone which is tied to a rope and is being swung in circles, a car turning through a curve in a race track, an electron moving perpendicular to a uniform magnetic field, and a gear turning inside a mechanism.
Since the object's velocity vector is constantly changing direction, the moving object is undergoing acceleration by a centripetal force in the direction of the center of rotation. Without this acceleration, the object would move in a straight line, according to Newton's laws of motion.

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  1. 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...
  2. 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...
  3. 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,
  4. Nabin kalauni

    Pulling a puck through the hole

    Homework Statement Its a classic problem about a puck that is rotating on a frictionless tabble with a velocity v1 and radius r1. It is is connected to a string which runs through a hole a the centre of the table. The string is pulled from below until the radius decreases to r2. Find the work...
  5. LouysHong

    I Launching a particle at the highest point inside a sphere

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  6. T

    Analyzing Forces in Circular Motion: Ramp and Ball System

    Homework Statement A ball rolls down a ramp which forms a quarter circle of radius 0.5m. The ball weighs 25g. The bottom of the ramp is 1.5m above the floor. Assume no friction between the ball and the ramp. Assume no air resistance. what is the force exerted by the ramp on the ball? whatis...
  7. 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...
  8. physicaled

    Circular Motion: Ball on String

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  9. 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...
  10. Ashton Herbert

    A question regarding the Centripetal force

    Hi, if you consider a ball, with mass m, rolling down the outer surface of a hemisphere with radius r, why is it that if you consider the forces acting upon the ball and resolve in a direction, the equation formed is: mgcos(x) - R = m(v^2)/r If you rearrange that, it would appear that the...
  11. V

    Point of Maximal Tension for Vertical Circular Motion

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  12. 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...
  13. Khunpol Jermsiri

    Circular motion object falling in the circle

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  14. 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...
  15. B

    Tangential and centripetal acceleration in circular motion

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  16. Rodriesk

    Magnitudes and Directions In Uniform Circular Motion

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  17. PhysicsCollegeGirl

    Amusement Rotor Ride Explanation

    1. Homework Statement An amusement park ride consists of a large vertical cylinder that spins about its axis fast enough that any person inside is held up against the wall when the floor drops away (see figure). The coefficient of static friction between person and wall is μs, and the radius of...
  18. J

    Kinetic Energy in Circular Motion: Is 1/2 m v^2 Still Applicable?

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  19. Arman777

    Rotational Motion - Understanding the Idea

    1- I am trying to understand the rotational motion and In most books there's ##\vec θ## unit vector which its, ##\vec θ=(-sinθ,cosθ)## I can see that If ##\vec r## unit vector is,##\vec r=(cosθ,sinθ)## then , ##\frac {d\vec r} {dt}=\vec θ## Like calculating ##\vec v=\frac {d\vec r}...
  20. 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...
  21. F

    Circular motion: ring on string

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  22. 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...
  23. J

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

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  24. Clara Chung

    Question about circular motion on a horizontal road

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  25. Schaus

    Roller Coaster Physics: Calculating Energy, Speed, and Force

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  26. Kernul

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

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  27. E

    What distance is needed for a body to spin in circular motion with a spring?

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  28. C

    Kepler's Law for finding velocity

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  29. V

    Two particles undergoing circular motion

    Homework Statement Homework EquationsThe Attempt at a Solution I am actually stumped by this seemingly simple problem . Since both the particles are moving , in order to calculate angular velocity of Q with respect to P looks to be difficult as the relative velocity of Q w.r.t P is...
  30. M

    Circular motion: Speed, velocity for car on a semi-circular path

    Homework Statement A car moves from X to Y along a semicircular path. The radius of the path is 250 m and the time taken to complete the trip is 50 s. What is the magnitude of the average velocity and the magnitude of the average speed? can you please explain? <3 Homework Equations v = wr = 2π...
  31. Likith D

    Do objects in circular motion also *have* to undergo rotation?

    1. 2. Well, these are two pics on circular motion, i found on net... If the objects had a zero rotational motion before circular motion, and the next moment suddenly a force acts ( perpendicular to their linear momentum ) such that they move in circular motion,... which of these pictures...
  32. T

    What charge would have to be fixed at the origin?

    Homework Statement A ball of mass m is attached to a rope of length L which has one end at the origin; the ball moves in a horizontal circle at constant speed v0 on a frictionless plane; the velocity is always at 90◦ to the rope. The ball has a charge q, and moves in a constant magnetic field...
  33. Sarina3003

    Understanding Uniform Circular Motion to Solving Problems

    :H:H:H1. Homework Statement Homework Equations equations is not needed here The Attempt at a Solution I have no idea :( Please help me![/B]
  34. ashraful

    Acceleration in circular motion

    Homework Statement In the case of circular motion,the direction of the velocity is changing in every moment.So,there is a angular accelleration here.What is the direction of this accelleration? Homework EquationsThe Attempt at a Solution
  35. C

    Average velocity vector of non-uniform circular motion?

    Homework Statement A particle starting from rest revolves with uniformly increasing speed in a clockwise circle in an xy plane. The center of the circle is at the origin of an xy coordinate system. At t=0, the particle is at x=0.0m, y=2.0m. At t=2.0s, it has made one-quarter of a revolution and...
  36. Robzoid

    Movement caused by Centripetal Force

    I've been thinking about centripetal force and circular motion. I know that an object experiencing circular motion has a velocity vector tangential to the circular path and an acceleration vector perpendicular to its motion, pointing towards the center of the circle. What I don't get is why...
  37. S

    Circular Motion, an object attached by a string to a motor

    Homework Statement A pendulum traveling at constant speed along a circular path Determine the angle that the string makes with the vertical. T[/B]he length of the string was measured to be 60 cm. The period was measured to be 1.41 s The frequency was found to be 0.709 2. Homework Equations...
  38. SnoppDoge

    Solving circular motion problem

    Homework Statement Our teacher gave us a formula to solve it by creating a computer program but the problem is I'm not good at physics. I need to know what is Fc,Mr,Fk etc.. 1.) Fc = Mr(theta - Oo) ^ 2 / (t - tn) ^ 2 2.) M = Fk / Mk(m)(g)cos(theta) Homework EquationsThe Attempt at a...
  39. L

    What is the tension in a hockey puck swung in a horizontal circle?

    Homework Statement A hockey puck with mass 200 g is attached to a rope of length 62.0 cm and swung in a horizontal circle against the ice at a rate of 58.0 rpm. Assuming the ice is frictionless, what is the tension in the rope? Homework Equations FT = mω2r The Attempt at a Solution 58rpm =...
  40. S

    Ice on an inverted bowl: Radial force?

    Hello! I am just stuck on one part of this question and would be grateful for any help. Question A small block of ice slides from rest from the top of an inverted frictionless bowl of radius R (above right). How far below the top x does the ice lose contact with the bowl? Equations mgx =...
  41. Giannakoulis

    Problem in a circular motion (find the max Frequency)

    In the figure below we put a small coin on a disc, which rotates at constant frequency f, at a distance D=0.2m by the disc rotation axis. If the coefficient of friction is μ=0.5, then what is is the maximum frequency that can have the disc so that the currency does not slip? g=10 m/sec^2 Anyone...
  42. A

    Uniform Circular Motion Problem. Help

    Homework Statement A stone tied to a string with length 1.10 m is whirled in a circle both horizontally and vertically with the same constant speed. In the vertical case the maximum tension in the string is 15.0% larger than the tension that exists when the string was horizontal. Determine the...
  43. A

    Uniform Circular Motion Problem

    Homework Statement 1. A car is safely negotiating an unbanked circular turn at 21 m/s and the maximum static force acts on the tires. Suddenly a wet patch on the road reduces the static frictional force by a factor of three. At what speed must the driver slow to in order to safely continue on...
  44. B

    Calculating Tension and Acceleration in a Circular Motion

    Homework Statement A small ball with mass m=1.1kg moves on the end of a string with length L=2.9. The string is anchored at point A and travels in a horizontal circle as shown. The string is at and angle of 36 degrees from the vertical. What is the string tension as the ball swings in this...
  45. R

    What cause the pizza dough go to circular motion

    my teacher said it is the intermolecular forces between the particle but i don't agree with them so anyone can help me .
  46. D

    Average acceleration of the a particle in circular motion

    Homework Statement A particle of mass ##m## moves along a circle of radius ##R##. The modulus of the average vector of the force acting on the particle over the distance equal to a quarter of the circle is: zero if the particle moves with uniform speed ##v##. ##\dfrac{\sqrt2mv^2}{\pi R}## if...
  47. Eclair_de_XII

    Calculating velocity needed for uniform circular motion?

    Homework Statement "Figure 8-32 shows a pendulum of length ##L=\frac{5}{4}m##. Its bob (which effectively has all the mass) has speed ##v_0## when the cord makes an angle ##\theta_0=40°## with the vertical. (a) What is the speed of the bob when it is in its lowest position if...
  48. J

    A Gravitational Radiation Power of Object in Forced Circular Motion

    I am curious as to the formula for radiative power due to a single object in forced circular motion. In particular, I am interested in the power of gravitational radiation for volumetric invariant mass densities for both the low density Newtonian limit and the high density general relativistic...
  49. N

    Tension in an object moving with circular motion

    Homework Statement An object of mass 0.8kg is whirled round in a horizontal circle of radius 2m with a constant speed of 15ms-1. Calculate the tension in the string. The Attempt at a Solution So far I have calculated that the angular velocity is 7.5rads-1, the frequency is 1.19Hz and the time...
  50. K

    How to Calculate Angular Displacement in Circular Motion?

    [moderator's note: Thread moved from forum General Physics, so no template shown] The angular velocity of a process control motor is (10−1/2t^2) rad/s, where t is in seconds. a. At what time does the motor reverse direction? I got 4.5 s which is correct b. Through what angle does the motor...
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