Uniform circular motion Definition and 312 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. C

    Finding Apparent Weight with Uniform Circular Motion

    Homework Statement A ferris wheel with a radius of 14.0 m rotates at a constant rate, completing three revolutions in 50.0 s. What is the apparent weight of a 60.0 kg passenger when she is at the top of the wheel? Given choices: 532 N, 452 N, 562 N, 625 N, 469 N Homework Equations...
  2. S

    Special relativity- Uniform circular motion.

    Homework Statement Imagine two clocks that both perform uniform circular motion of radius a in the x-y plane, but in opposite directions: xμ(u) ={t, a cos(ωt),±a sin(ωt), 0}. Suppose these clocks are synchronized to agree when they are coincident at x = a at t = 0. How much time elapses until...
  3. E

    Uniform circular motion particle problem

    Homework Statement At t1 = 3.00 s, the acceleration of a particle moving at constant speed in counterclockwise circular motion is a1=(6m/s2)i+(5m/s2)j At t2 = 4.00 s (less than one period later), the acceleration is a2=(5m/s2)i-(6m/s2)j The period is more than 1.00 s. What is the radius of...
  4. S

    Uniform circular motion lab question

    Could any here smart people help me with the Lab question: 3. Why do we measure the period by timing 25 revolutions? Why not one revolution or 100 revolutions? This is from http://www2.sunysuffolk.edu/denicog/labs/lab11_132.pdf Lab from Uniform Circular motion. Thank you so much!
  5. T

    Uniform circular motion with constant upward velocity.

    Homework Statement It is common to see birds of prey rising upward on thermals. The paths they take may be spiral-like. You can model the spiral motion as uniform circular motion combined with a constant upward velocity. Assume a bird completes a circle of radius 6.00m every 5.00s and rises...
  6. A

    Radius as a function of Uniform Circular Motion

    How exactly does radius affect centripetal acceleration? In one formula we have (a=v^2/r) which implies inversely proportional, while in the other we have (a=(w^2)*r) which implies directly proportional. I understand that increasing r increases velocity (v=w*r) which means the right answer is...
  7. E

    Uniform Circular Motion - Finding Fc/Ft without mass

    Homework Statement A boy ties a rock to a 0.95 m string and swings it in a horizontal circle directly over his head so that it completes one revolution every 0.75 s. What is the tension in the string? So we know r and we can calculate V, but that's all I can deduce Homework Equations...
  8. H

    Uniform Circular Motion Derivation of Radial Acceleration

    Homework Statement I am trying to derive the formula a_r=\frac{v^2}{r} for uniform circular motion (for personal understanding, this is not an assignment). But am having some difficulty. I have seen other proofs, but I want to know why my approach is wrong. The Attempt at a Solution...
  9. W

    Uniform Circular Motion of a race car

    Homework Statement A 990-kg race car can drive around an unbanked turn at a maximum speed of 42 m/s without slipping. The turn has a radius of 140 m. Air flowing over the car's wing exerts a downward-pointing force (called the downforce) of 12000 N on the car. (a) What is the coefficient of...
  10. U

    What Speed Causes Weightlessness on a Circular Hill?

    Max. speed you can drive on a circular hill an still be in "Uniform Circular Motion" Homework Statement The top of a hill is in the shape of a circle of radius 25 meters. Homework Equations a) What is the normal force that the road exerts on an 1800kg car as it tops the hill with a...
  11. A

    Uniform Circular Motion of Swinging Objects

    I am very confused with a particular aspect of part of my physics curriculum. Let's say there is an object swinging on a rope swinging in a circular motion. The mass of the object, length of rope, and angle of rope relative to y-axis are known. How does one derive the tension of the rope...
  12. E

    Calculating g using horizontal uniform circular motion

    Hi! I’ve recently done an experiment that I didn’t completely understand and now it seems I’ve lost all my notes as well (the notes written down from the teacher’s board, with a formula I really need, but didn’t understand). This work is supposed to be completed during the summer holiday, so I...
  13. A

    Uniform Circular Motion Homework: Maximum Speed and Tension Calculation

    Homework Statement Hi Can anyone help with this question? It will be highly appreciated. An object of mass 6kg is whirled round in a vertical circle of radius 2m with the speed of 8m/s. If the string breaks when the tension in it exceeds 360N, calculate the maximum speed of rotation and...
  14. B

    Understanding Uniform Circular Motion: Explanation & Diagrams

    I am reading about uniform circular motion currently, but I am sort of confused by this paragraph: "We next determine the magnitude of the centripetal centripetal (radial) acceleration, ar. Because CA in fig. 5-2a is perpendicular to V1, and CB is perpendicular to V2, it follows that the...
  15. V

    Uniform circular motion (centripetal acceleration & force)

    Imagine a body moving to the right with velocity v, I then apply a force that accelerates the body leftwards by v and downwards by v. After one second, the body has stopped moving to the right and is only moving downwards with velocity v. Then, while I keep accelerating the body to the left...
  16. J

    Uniform Circular Motion (free-body diagram)

    Homework Statement Curved portions of highways are always banked (tilted) to prevent cars from sliding off the highway. When a highway is dry, the frictional force between the tires and the road surface may be enough to prevent sliding. When the highway is wet, however, the frictional force...
  17. N

    Uniform Circular Motion; Need help with deriving equations.

    Homework Statement Hi I'm doing a physics lab about uniform circular motion to measure frequency and to compare it to mass,radius and force tension. (A & B) I did (C,D, E) I need help (a) What variables are being measured / manipulated in this lab? What type of relationship is being...
  18. F

    Uniform circular motion - 2 dimensional - 2 forces

    An object moves in the xy-plane in a uniform circular motion. We know that there is two forces action upon the object. One we have that is F1, F2 is unknown. Both vectors speed : 4m/s radius : 4m mass : 1kg F1 : 10 i N (i as in x-direction vector) F2 : ? (bound to be in the xy-plane)How do I...
  19. M

    Uniform circular motion question

    A ball of mass m is attached by two strings to a vertical rod. as shown above. The entire system rotates at constant angular velocity about the axis of the rod. a)Assuming ω is large enough to keep both strings taut, find the force each string exerts on the ball in terms of ω, m, g, R, and ...
  20. E

    Uniform Circular Motion Bicycle Tire

    Homework Statement A spot of paint on a bicycle tire moves in a circular path of radius .33m. When the spot has traveled a linear distance of 1.66m, through what angle has the tire rotated? Homework Equations v=rw w=2∏/T The Attempt at a Solution 1.66=2∏/T 1.66T=2∏ 100∏/83
  21. E

    Uniform Circular Motion in a Watch

    Homework Statement The second hand on a watch has a length of 4.5mm and makes one revolution in 60s. What is the speed of the end of the second hand as it moves in uniform circular motion? Homework Equations ac=v^2/r The Attempt at a Solution ac=v^2/4.5
  22. E

    Instantaneous Acceleration for Uniform Circular Motion

    Homework Statement A normally functioning clock has a radius of 30cm. What is the average acceleration in the first 15 seconds if the second hand starts at 12? What is the instantaneous acceleration when the second hand is at 12? Homework Equations v = d/t a = Δv / Δt limit as Δt...
  23. M

    Can Frequency Influence Circular Motion and Centripetal Force?

    I need these Questions answers in 2 hours! :p Any help would be greatly appreciated. Homework Statement Question 3 Mathematically derive a relationship between the speed v, of a body moving in a circle of radius r, and the frequency f, of the revolutions. Question 4 Use your results...
  24. M

    History of Uniform Circular Motion

    Anyone know how the theory of Uniform Circular Motion was discovered? I know Newton invented the word "centripetus", Latin for Centripetal but that's about it. I can find history on the pendulum but nothing for uniform circular motion. Could you give me some names? Or links to some...
  25. K

    Force on Stopper in UCM & Hanging Washer Relationship

    Homework Statement What is the relationship between the weight of the hanging washers and the force acting on the stopper by the string? Here is the diagram provided by the book: http://www.goodreads.com/photo/user/5034346-kylaia-formerly-known-as-klymene?photo=454140 It also says to...
  26. M

    Uniform Circular Motion - Finding Linear Speed

    Homework Statement The Bohr model of the hydrogem atom has one electron rotating around its center. If it has a radius of 5.29 * 10-11 m. And the mass of the electron is : 9.11 * 10-31. And the electrostatic force between the orbiting electron and the center proton is 8.20 * 10-8. Find: 1)...
  27. L

    Finding the position vector of uniform circular motion

    Homework Statement Write an equation for one component of the position vector as a function of the radius of the circle and the angle the vector makes with one axis of your coordinate system. Calculate how that angle depends on time and the constant angular speed of the object moving in a...
  28. A

    Uniform Circular Motion Free Body Diagrams

    Homework Statement A circular-motion addict of mass 82.0 kg rides a Ferris wheel around in a vertical circle of radius 14.0 m at a constant speed of 7.10 m/s. (a) What is the period of the motion? What is the magnitude of the normal force on the addict from the seat when both go through (b)...
  29. C

    What is linear acceleration in uniform circular motion?

    What is "linear acceleration" in uniform circular motion? Yesterday, I took an exam and it was asked a concept that we hadn't studied, at least in the way it was written. The exercise explained that a circular motion was decreasing its velocity, and we had to be able to identify which of the...
  30. J

    Uniform circular motion formula when the object submarge in acid?

    hello friend, this is my first post please go easy on me. the best way i can express my problem is below. I attach a pic to give you a better idea. A is a circular disk with 4.5" diameter, DISK A is driven by C which is connected to a DC motor. B is a pin diameter of 1 mm which is going to...
  31. T

    Theory Question - Uniform Circular Motion

    -Question Removed-
  32. T

    Help with the non uniform circular motion ?

    I am given the moment of inertia of the system ( a fan) and the question asks for me to find the angular acceleration "after the fan is turned on, it takes t = 3.6 s and a total of 12 revolutions to accelerate up to its full speed" ? How I went about solving is that.. I simply converted the rev...
  33. M

    Two masses connected by a string uniform circular motion. HELP

    Two masses connected by a string uniform circular motion. HELP! :) Homework Statement A puck of mass m1 is tied to a string and allowed to revolve in a circle of radius R on a frictionless, horizontal table. The other end of the string passes through a small hole in the center of the table...
  34. M

    Uniform circular motion question

    Please look at the picture... It is of a blue object in four locations that is swung around with a rope ( red line ) in a circle with constant velocity... I wanted to know if my diagrams are correct for each separate location... and I was hoping someone could check my work below to tell me...
  35. A

    How can I solve for the mass and radius in this uniform circular motion problem?

    Homework Statement A toy airplane is tied to the ceiling with a string. When the airplane's motor is started, it moves with a constant speed of 1.01 m/s in a horizontal circle, as illustrated in the figure. If the angle the string makes with the vertical is 38°, and the tension of the string...
  36. N

    Uniform Circular motion problem,

    1. At a distance of 25km from the eye of a hurricane, the wind is moving at 180km/h in a circle. What is the magnitude of the centripetal acceleration, in meters per second squared, of the particles that make up the wind? Homework Equations Ac=V^2/r = 4∏^2r/T^2 = 4∏^2rf^2 The Attempt...
  37. S

    Acceleration in Uniform Circular Motion

    Homework Statement What is the acceleration (in m/s^2) of a 10 kg mass moving with speed 2 m/s in uniform circular motion about a circle of radius 2m? Homework Equations F=ma a=v^2/r in uniform circular motion The Attempt at a Solution Seems simple enough. To find the...
  38. A

    How to Find Radial and Tangential Acceleration in Non-Uniform Circular Motion?

    Homework Statement car travels in a flat circle of radius r. at certain point instantaeous velocity is 24 m/s west and the total acceleration is 2.5 m/s2 53 degrees north of west. find radial and tangential acceleration. and periodHomework Equations ar= 2.5cos37 at=2.5sin37 r=24 x 24/ar T=...
  39. P

    How is tangential accleration zero in uniform circular motion?

    How is tangential accleration zero in uniform circular motion?? Homework Statement the magnitude of tangential velocity is same but the directions are different..so how can the tangential acceleration be zero?? Homework Equations The Attempt at a Solution
  40. B

    Dynamics of uniform circular motion

    A special electronic sensor is embedded in the seat of a car that takes riders around a circular loop-the-loop ride at an amusement park. The sensor measures the magnitude of the normal force that the seat exerts on a rider. The loop-the-loop ride is in the vertical plane and its radius is 21 m...
  41. B

    Uniform circular motion, trapeze artists problem

    Lewis is a trapeze artist. He is hanging upside down on a swing bar; he is holding on to the swing bar with his knees. Lewis is holding his partner Amanda below him, who weighs 475 Newtons. Assume that Amanda moves on a circle that has a radius of 6.50 meters. At a swinging speed of 4.00 m/s...
  42. B

    Uniform circular motion, earth's rotation

    The Earth rotates once per day about an axis passing through the north and south poles, an axis that is perpendicular to the plane of the equator. Assuming the Earth is a sphere with a radius of 6.38 x 106 m, determine the speed and centripetal acceleration of a person situated at a latitude of...
  43. R

    Non Uniform Circular Motion w/ Calculus and Vectors

    Hello! I have a problem which is solvable using simpler methods, but I'm trying to use it as a bridge to understanding how to do these problems in a more rigorous setting. Homework Statement A train slows down as it rounds a sharp horizontal turn, slowing from 90 km/hr to 50 km/hr in the...
  44. J

    I with this Uniform circular motion problem

    Homework Statement An astronaut is standing in an space station that spins. The linear speed and the centripedal aceleration that he experiences are bigger on his feet than on his head. Scientific experiments have proved that a difference of (1/100 )g won't produce this inconveniet for...
  45. S

    Zero Normal force during uniform circular motion?

    I am learning uniform circular motion and the question says: A child on a sled comes flying over the crest of a small hill. His sled does not leave the ground but he feels the normal force between his chest and the sled decrease as he goes over the hill. Explain. Now, I know that normal force...
  46. J

    Question on uniform circular motion

    An Earth satellite moves in a circular orbit 589 km above Earth's surface with a period of 96.26 min. What are (a) the speed and (b) the magnitude of the centripetal acceleration of the satellite? I know I need the equations for 1) period and 2) centripetal acceleration and 3) r. 1) T=...
  47. O

    Friction on bicycle wheels in uniform circular motion

    On pedaling a bicycle along a straight line, the friction act forward on the rear wheel and act backward on the front wheel. If I turn its handlebar so that the front wheel is at a certain angle (say theta) and pedal it in uniform circular motion, what would be the direction of the friction...
  48. Femme_physics

    Uniform circular motion with a pendulum

    Homework Statement http://img685.imageshack.us/img685/9250/drawingmo.jpg In the drawing is depicted a pendulum hammer of an impact device (in both projections). The hammer is made out of shaft AB which upon it is held pendulum OM. At point M of the pendulum is a hammer. According to...
  49. Femme_physics

    Uniform circular motion problem

    Homework Statement http://img200.imageshack.us/img200/2524/drawingsave.jpg Weight W that's 15 [N] does circular motion around shaft AB in a frequency of 300 turns per minute A) calculate the max tension force on shaft CD [there's another clause, but I rather just try A for now]The Attempt at...
  50. Femme_physics

    Uniform circular motion - simple problem

    Homework Statement A girl is running around a circular fountain with a diameter of 6.5m. If it takes her 72 seconds to run all the way around, what's her angular speed? The Attempt at a Solution I appear to be getting a wrong answer: (look only at the thick black marker)...
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