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. N

    Circular Motion with static friction

    1. Homework Statement A bus passenger has her laptop sitting on the flat seat beside her as the bus, traveling at 10.0 m/s, goes around a turn with a radius of 25.0 m. What minimum coefficient of static friction is necessary to keep the laptop from sliding? Given: V = 10 m/s r = 25.0...
  2. T

    Calculating & Visualizing Motion: 2kg Circular Motion

    Homework Statement A body of mass 2kg performs circular motion about a point O. The radius of the circle is 0.4m and the mass completes 20 revolutions per minute.Calculate: 1) the angular veloicty. 2)the linear velocity. 3) the centripetal acceleration,and 4) the kinetic energy 5) Draw a...
  3. S

    What is the Angle of a Dust Speck on a Turntable After 8 Seconds?

    Homework Statement A turntable rotates counterclockwise at 78rpm, a speck of dust on the turntable is at 0.42rad at t=0 ,What is the angle of the speck at t = 8.0s ? Your answer should be between 0 and 2π rad Express your answer using two significant figures.Homework Equations θf-θi=ωt The...
  4. C

    Circular motion and tension of a stone problem

    1. Homework Statement [/b] A stone mass 284g is twirled at a constant speed 12.4m/s in a vertical circle of radius 0.850m. Find the tension in the string at the top and at the bottom of the revolution. What is the maximum speed the stone can have if the string will break when the tension...
  5. S

    Circular motion of ball and string question

    Lets say we have a ball on a string and we spin it around. The ball will undergo circular motion. The tension in the string is what provides the centripetal force, directed inwards. Then what would be the force directed outwards? (According to Newton's third law of motion). It can't be...
  6. S

    Connecting Newton's 3rd law of motion to circular motion

    I am confused about connecting Newton's third law of motion to circular motion. For example, the Moon goes around the Earth in a circular orbit. There is a centripetal force (caused by gravity) that pulls the Moon inwards. However according to Newton's First law, the law of inertia, the Moon...
  7. C

    What is the centripetal acceleration of the hammer in circular motion?

    Homework Statement An athlete whirls a 7.00 kg hammer tied to the end of a 1.3 m chain in horizontal chain. The hammer makes one complete revolution in 1.0 s. (A) What is the centripetal acceleration of the hammer? 51 m/s2 Homework Equations ac=4pi^2*r/r^2 The Attempt at a...
  8. Y

    Circular Motion and Oscillationshave been sick and am lost

    Homework Statement A particle begins at rest on a circular track and is subjected to a constant angular acceleration of magnitude α beginning when t=0s.(a) Show that the magnitudes of the tangential and centripetal accelerations of the particle are equal when t=(1/α )^(1/2) Independent...
  9. S

    Circular Motion: Net Force and Direction

    1. Homework Statement A 1500 kg car drives around a flat 200-m-diameter circular track at 25 m/s. What is the magnitude and direction of the net force on the car? What causes this force? 2. Homework Equations F=mv2/r 3. The Attempt at a Solution So I suppose the net force is...
  10. N

    Do you know of any questions regarding projectile and circular motion?

    Sorry not to follow the template, but I am seeking help finding practice problems, rather than asking for help on a specific question. I am specifically searching for a practice problem regarding both projectile and circular motion/centripetal acceleration. Furthermore, I would prefer...
  11. F

    Circular Motion of an amusement park ride

    In an amusement park ride called The Roundup, passengers stand inside a 15.9 m diameter rotating ring. After the ring has acquired sufficient speed, it tilts into a vertical plane (a) Suppose the ring rotates every 4.5 s. If a rider's mass is 69 kg, with how much force does the ring push on...
  12. Q

    Uniform Circular Motion: Solving for String Tension

    Homework Statement A ball of mass 4 kg on a string of length 1.5 m is being swung in a circle in the vertical plane at a constant speed of 10 m/s. Find the tension in the string at the bottom and top of the balls path Homework Equations ƩF = m(v^2/r) The Attempt at a Solution This is how I...
  13. W

    Circular Motion Rotational Axis

    Homework Statement Child P happens to be at a greater distance from the rotation axis than Child M. Which child has the greatest angular velocity? 2. The attempt at a solution Do they have the same angular velocity, and if they do can you please explain. Thank you.
  14. S

    Grade 12 Physics - Circular Motion - Universal Gravitation

    Homework Statement This question is from the Nelson Grade 12 Physics textbook. The force of attraction between masses m1 and m2 is 26N in magnitude. What will the magnitude of the force become if m2 is tripled, and the distance between m2 and m1 is halved? Homework Equations...
  15. H

    Vertical Circular Motion problem

    Homework Statement A motorcycle has a constant speed of 25.0m/s as it passes over the top of a hill whose radius of curvature is 126m. The mass of the motorcycle and driver is 342kg. Find the magnitudes of (a) the centripetal force and (b) the normal force the acts on the cycle Homework...
  16. J

    Circular motion ultra-centrifuge spin

    Homework Statement An ultra-centrifuge has a cylindrical disk mounted on an axle that is almost frictionless. The disk spins about an axis through its centre as shown. If the disk is spinning with an angular speed of 4.50 x 10^5 rad/s and the driving force is turned off, its spinning slows...
  17. S

    Particle in uniform circular motion

    Homework Statement A satellite is orbiting 600km above the Earths surface. The free fall speed is 8.21 m/s^2. The radius of Earth is 6400km. What is the satellites speed, and the time interval for one orbit around Earth. Homework Equations v = ((2)(PI)(r))/T ac = rw^2 w = (2)(PI)...
  18. klc2006

    Circular Motion of a Marble: What Determines the Speed at a Given String Length?

    Homework Statement You swing a marble with mass m attached to the end of a string in a horizontal circle as shown in the figure below. The angle that the string makes with the vertical is θ = 37°. (a) Find the speed of the marble when the string is 26.0 cm long.Homework Equations soh,cah,toa...
  19. P

    Pulley and Circular Motion: Exploring the Mechanics of Rotation

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  20. P

    Calculating Acceleration in Non-Uniform Circular Motion

    Homework Statement The Attempt at a Solution So I just want to ask any of you who know physics pretty well if I am on the right track on this question, so it is asking for the magnitude of the acceleration of the car, and the direction. The magnitude of acceleration is (v^2/R) v = velocity and...
  21. B

    Uniform Circular Motion A Jet Pilot

    Uniform Circular Motion "A Jet Pilot" Hi, my apologies if this has been posted before. I was just wondering if someone could help look over this question for me and confirm if I did it correct or not. It is a written homework rather than online so I can't check my answer to see if I did it...
  22. M

    Circular Motion: Deriving r for Two Objects on a String

    Homework Statement A small object of mass m1 moves in a circular path of radius r on a frictionless horizontal tabletop. It is attached to a string that passes through a frictionless hole in the center of the table. A second object with a mass of m2 is attached to the other end of the...
  23. N

    Circular motion: net work after one period

    Homework Statement "A 40 kg child sitting 6.0 m from the center of a merry-go-round has a constant speed of 6.0 m/s. The net work (in Joules) done on the child after making one complete circle on the merry-go-round is?"Homework Equations a=V^2/r F=ma C=2pi*r The Attempt at a Solution C ≈...
  24. S

    How Is Velocity and Acceleration Affected as a Carousel Slows Down?

    Homework Statement A carousel takes 1.5 min to complete one revolution while rotating at a constant rate. A person rides on the carousel platform at a distance 3.2m from the center. (a) From its state of constant rotation, the carousel then uniformly slows to a stop in time (delta t). Produce...
  25. A

    Circular Motion with constant angular acceleration

    Homework Statement An object travels counterclockwise on a circular path with radius R and constant angular acceleration α , so that vector r(t) = R cos(αt^2/2) i^+ R sin(αt^2/2) j^  Homework Equations b. Find the time T when the object made a single revolution and returned to...
  26. C

    Speed Pertaining to Circular Motion

    Units for Speed Pertaining to Circular Motion Hi, So v=ω*r Where v = velocity in m/s ω = angular velocity in rad/s r = radius in m But I am confused...the units don't match! What happens to the rad? m/s = (rad/s)*s My textbook doesn't explain it, it simply does calculations...
  27. M

    Finding the Velocity and Acceleration of a Car in Circular Motion

    Homework Statement A car enters the circular road with radius r = 200m at a speed of v = 80km/h. A radar gun at O needs to rotate with constant angular acceleration d^2θ/dt^2 = 0.025 rad/s2 to follow the motion of the car along the circular road. a) Determine the acceleration of the car...
  28. skate_nerd

    MHB Proofs regarding uniform circular motion in vectors

    Just started this Analytical Mechanics class, so I figured this question should go here... I've been pretty stuck with a problem. I felt like I totally knew what I was doing but I've become very stumped. We're given the vector for general circular motion...
  29. T

    Circular Motion Problem 2: Help with Solving | Physics Forum

    Hi friend the problem is as follows: Attempt: Please friends help me in this. Thank you all in advance
  30. T

    What is the Solution to a Confusing Circular Motion Problem?

    The problem is as such : Attempt to the problem: The answer is confusing Option D Thank you all in advance.
  31. T

    Solving Circular Motion Problems | Book Answer Included

    The problem is : Attempt: According to book answer is option A Thank you all in advance
  32. M

    Doubt in uniform circular motion

    why are we considering speed is constant to find velocity a particle in uniform circular motion, is it possible for a particle in a circular motion to have constant velocity?
  33. C

    Help With Circular Motion Doubts

    Hello! I have a few doubts in circular motion and I'd really appreciate your help :) 1) There is a statement in my book ( I have attached images - the first one) according to which the only horizontal force towards the center on the vehicle is friction. I know that some centripetal force is...
  34. J

    Is uniform circular motion perpetual?

    If i took my pencil to a place in space without gravity or air resistance and i spun it, would it spin forever? I mean its undergoing a centripetal acceleration, so energy has to come from somewhere to keep it spinning right? (and of course this is not meant to be an idea for perpetual motion, i...
  35. M

    Archived Simple roulette in terms of circular motion

    Homework Statement I am trying to understand game of roulette through kinematic equations of circular motion. Roulette is game where a ball spins in circular motion. Initially it is accelerated such that velocity of ball increases with time however after reaching its peak value it starts to...
  36. A

    Circular Motion Homework: Plane at 200m/s, R Radius to Zero Weight

    Homework Statement A plane is traveling at 200 m/s following the arc of a vertical circle of radius R. At the top of its path, the passengers experience "weightlessness" .To one significant, what is the value of R ? Homework Equations Mv^2/R=Mat , N=mg(1+at/g) Velocity orbit =...
  37. O

    Acceleration in circular motion

    Hello, Regarding acceleration in circular motion, my textbook says the total acceleration of an object traveling in a circular path, can be computed by: a = \sqrt{a^2_c + a^2_t} and can be proved by pythag. thm. Can someone help me understand this intuitively? Thanks.
  38. andyrk

    Radial acceleration in uniform circular motion

    Why is there only a radial component of acceleration present if a body is undergoing uniform circular motion whereas in non uniform circular motion both tangential and radial component of acceleration are present?
  39. N

    Uniform Circular Motion extended response

    This began as homework that our Physics teacher set us. However, for some reason he decided no to collect it. I am curious as to whether or not this display my understanding of the topic well as communication is main area my teacher believes I need improvement in. Homework Statement Write a...
  40. andyrk

    Understanding Uniform Circular Motion: Exploring Centripetal Acceleration

    In uniform circular motion only a radial component of acceleration is present i.e centripetal acceleration. So why doesn't the particle following uniform circular motion go radially inwards due to radial acceleration?
  41. W

    Relative velocities of two particles in circular motion

    Problem: Consider two particles a and b moving in opposite directions around a circle with angular speed ## \omega ##. At ## t = 0 ## they are both at the point ## \vec{r}=\ell \hat{j} ##. Find the velocity of a relative to b if the radius of the circular path traced out by the...
  42. K

    Physics circular motion and gravity help please

    physics circular motion and gravity help please :( Homework Statement 1. a) A solid homogeneous sphere of mass M = 4.80 kg is released from rest at the top of an incline of height H=1.35 m and rolls without slipping to the bottom. The ramp is at an angle of θ = 25.7o to the horizontal...
  43. K

    Circular motion and gravity help

    Homework Statement 1. The mass of a star is 1.830×1031 kg and it performs one rotation in 37.30 days. Find its new period (in days) if the diameter suddenly shrinks to 0.850 times its present size. Assume a uniform mass distribution before and after. 2. A pulley with mass Mp and a radius...
  44. K

    Physics help, circular motion and gravity

    anything is appreciated! 1. The mass of a star is 1.830×1031 kg and it performs one rotation in 37.30 days. Find its new period (in days) if the diameter suddenly shrinks to 0.850 times its present size. Assume a uniform mass distribution before and after. 2. A pulley with mass Mp and a...
  45. K

    How Do You Calculate Motion and Forces in Physics Problems?

    physics circular motion and gravity help please :( 1. a) A solid homogeneous sphere of mass M = 4.80 kg is released from rest at the top of an incline of height H=1.35 m and rolls without slipping to the bottom. The ramp is at an angle of θ = 25.7o to the horizontal. Calculate the speed of the...
  46. Nugso

    Uniform Circular Motion

    Homework Statement An object is in uniform circular motion. As the time passes by, its mass decreases. ( It has Co2 in it, and it evaporates) What will happen to the object's velocity and angular momentum? Homework Equations F = mV²/r, L = mvr The Attempt at a Solution...
  47. A

    Uniform Circular Motion Question (Mechanics/Physics I)

    Uniform Circular Motion Question Please Help! (Mechanics/Physics I) A car initially traveling eastward turns north by traveling in a circular path at uniform speed as in Figure P6.10. The length of the arc ABC is 200 m, and the car completes the turn in 34.0 s. (figure attached as...
  48. L

    Nonuniform Circular Motion - Find Maximum Total Acceleration

    Homework Statement A turntable is rotating at a constant angular velocity of ω = 4.0 rad/s in the direction of a clockwise fashion. There is a ten-cent coin on the turntable, at a distance of 5 cm from the axis of rotation. Consider the time interval during which the turntable is...
  49. sa1988

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    Hi all, new user here and straight in with a question to help me understand something. Not sure if I'm in the right sub-forum but oh well. Regarding circular motion and centripetal acceleration, we're given the classic example of a cyclist leaning into a corner to create a general equilibrium...
  50. A

    Direction of force acting on a body in uniform circular motion?

    Direction of force acting on a body in uniform circular motion?? Hello Sir/Ma'am I'm a a novice. I joined this forum to clear my doubts and improve my physics. Here is my question.. " We generally say, frictional force always acts in a direction, opposite to the direction of motion of a body...
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