What is Pendulum: Definition and 1000 Discussions

A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force acting on the pendulum's mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period. The period depends on the length of the pendulum and also to a slight degree on the amplitude, the width of the pendulum's swing.
From the first scientific investigations of the pendulum around 1602 by Galileo Galilei, the regular motion of pendulums was used for timekeeping, and was the world's most accurate timekeeping technology until the 1930s. The pendulum clock invented by Christiaan Huygens in 1658 became the world's standard timekeeper, used in homes and offices for 270 years, and achieved accuracy of about one second per year before it was superseded as a time standard by the quartz clock in the 1930s. Pendulums are also used in scientific instruments such as accelerometers and seismometers. Historically they were used as gravimeters to measure the acceleration of gravity in geo-physical surveys, and even as a standard of length. The word "pendulum" is new Latin, from the Latin pendulus, meaning 'hanging'.

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  1. A

    Why does the acceleration of a pendulum depend on Rθ and not x?

    Okay I hope I can write this so it makes sense what I am thinking. For a pendulum you have: Fres = -mgsinθ And Fres points along the circumference: So: mRθ'' = -mgsinθ I wonna discuss this property that you can just express the acceleration as Rθ''. In a cartesian coordinate frame...
  2. P

    Questions - solving pendulum period of rotation

    Questions -- solving pendulum period of rotation Physical pendulum has a period of rotation that changes by Changing the temperature. According to the above show that the frequency shift of the pendulum would be: I have 2 questions,first solving the above question and the second how...
  3. Y

    Period of a Physical Pendulum: Finding T for a Uniform Disk

    Homework Statement A uniform metal disk (M = 9.81 kg, R = 8.99 m) is free to oscillate as a physical pendulum about an axis through the edge. Find T, the period for small oscillations. Homework Equations I (uniform disk, with axis through center of mass) = (1/2)MR^2 T = 2π√(I/mgd)...
  4. S

    Pendulum suspended from Horizontal rotating hoop

    Homework Statement A massless hoop is suspended horizontally and is free to rotate about a vertical axis through its center with a constant angular velocity (omega). Attached to the edge of the hoop is a simple pendulum that is restricted to oscillate in only the radial direction. find the...
  5. T

    Pendulum problem, need to be checked

    A pendulum of length 0.6m swings so that at the bottom of its swing, it contacts a peg located 0.4m from the pivot point (0.2m from the CG). At what angle from vertical must the bob be released so that it will just make a revolution around the peg? F = Mg = M*V^2/r Mg (l-l cos x) = 1/2...
  6. A

    Generalized coordinates - Rotating pendulum

    My question is kinda simple but it has been causing me some trouble for a while. In the problem of the pendulum rotating about an axis, why isn't the angle of rotation about the axis a generalized coordinate? The doubt appears when i try to write the hamiltonian for the system and i don't know...
  7. J

    Solving Energy Conservation for Pendulum Movement

    Homework Statement Conservation of energy: looking for equations to solve the following Homework Equations A pendulum with length l = 0.50 m and with a negligible mass. The string is attached to a fixed point A and the pendulum swings in a vertical plane. The pendulum has a speed v = 2.15...
  8. Q

    Solve Pendulum Problem: Avg Horiz Speed of Gorilla in m/s

    Homework Statement A gorilla is swinging on vines. Each vine is 30 meters long and the gorilla catches each vine when it is at rest 15 degrees to the left of the (downwards) vertical, swings on it until it stops at an angle of 15 degrees to the right of vertical, and then grabs the next vine at...
  9. E

    Eddy Current Braking of a Simple Pendulum

    I'm setting up an experiment and I 'd like to somehow quantify the effects of magnetic braking on a simple pendulum. At the moment, I have a curved sheet of Aluminium that I will swing freely between two magnets set up in yoke (horseshoe magnets). The magnets induce eddy currents in the...
  10. M

    Calculate RPM From Pendulum Swing Set

    Pendulum into RPM?? Hi I'm trying to throw together a concept design for a swing set which can convert kinetic energy into mechanical energy. In short I would like a swing set, using one way roller bearings to drive an output shaft but am unsure where to start. If I have a mass (m)...
  11. S

    Simple Pendulum nonlinear second order differential equation

    Homework Statement given: dt=-\frac{1}{2}\sqrt{\frac{l}{g}}\frac{d\theta}{\sqrt{sin^2(\alpha/2)-sin^2(\theta/2)}} make the change of variables sin(\theta/2)=sin(\alpha/2)sin(\phi) to show that: dt=-\sqrt{\frac{l}{g}}\frac{d\phi}{\sqrt{1-k^2sin^2(\phi)}} where k=sin(\alpha/2) Homework...
  12. R

    REAL QUICK question about how to solve for the period of a simple pendulum?

    REAL QUICK question about how to solve for the period of a simple pendulum? For part a, I tried using the formula: T = 2π√(L/g) I did, T = 2π√(53.4/9.8) T = 2π√(5.44) T = 2π(2.33) T = 14.6 s But that's wrong... Help please?
  13. H

    Relating moment of Inertia and pendulum oscillation

    I took a picture of the question to help. I know that the moment of inertia for a rod (at one end, not the center) is: 1/3ML^2 And I know that the period of oscillation is: T=2∏√(L/g) But I don't know how to relate them... I tried doing Torque=Iα=Fdcosθ and solve in terms of...
  14. 9

    What is the Maximum Height of a Pendulum with Given Initial Conditions?

    I'm trying to solve this problem via Lagrangian mechanics, but I'm having trouble correctly formulating the problem, I'm hoping one of you kindly people can show me where I'm going wrong. A pendulum bob of mass m hangs in the equilibrium position from a light, inextensible string of length l...
  15. R

    Solving for Velocity and Describing Motion of a Spring-Mass System

    #7. This is what i tried to do... but I got it wrong :( Please help T ≈ 2π√(L/g) 1.31 = 2π√(L/9.81) 1.31/2π = √(L/9.81) 2.057 = √(L/9.81) 2.057² = L/9.81 4.2343 = L/9.81 4.2343(9.81) = L 41.54/1000 = L 0.0415 = L "INCORRECT: Your response differs from the correct answer by more than 100%. "
  16. Z

    Finding charges in a pendulum in equilibrium

    (solved) Finding charges in a pendulum in equilibrium Homework Statement Two small metallic spheres, each of mass 0.20 g, are suspended as pendulums by light strings from a common point. The spheres are given the same electric charge, and it is found that the two come to equilibrium when...
  17. J

    Find coefficient of kinetic friction between a bullet and a pendulum

    Homework Statement A bullet collides and embeds itself into a block hanging from a rope. The block and embedded bullet swing out to an angle of 10 degrees. If the bullet plows 2 cm into the block before stopping, what is the coefficient of kinetic friction between the block and the bullet...
  18. V

    Calculating Tension in a Pendulum: Problem-Solving Tips and Tricks

    Homework Statement A mass at the end of a light rigid rod of length (r) is dropped from a position vertically above the pivot point. What is the tension in the rod when the mass reaches the lowest point of its swing? Homework Equations PEi +KEi = PEf +KEf and maybe also Acen = V^2/r, maybe...
  19. C

    Restoring force on a pendulum

    Homework Statement What is the net force done on a driven pendulum? Homework Equations Fd=mk (driving force) Fg=mg (Gravitational force) Fr=? (Do I need to include this?) The Attempt at a Solution Fnet = Fd + Fg = mk + mg I'm not sure if I need to include the restoring force...
  20. V

    Pendulum Problem: Solving for Angular Velocity (ω)

    Homework Statement A small object of mass m, on the end of a light rod, is held horizontally at a distance r from a fixed support. The object is then released. What is the angular velocity, ω, of the mass when the object is at the lowest point of its swing? Homework Equations This is my...
  21. C

    How to find the kinetic energy of a pendulum?

    The potential energy can be obtained with the equation Fnet = ∇U Where Fnet is the sum of all the forces acting on the pendulum. How can we obtain kinetic energy when we don't know the mechanical energy or the velocity?
  22. D

    Time it takes a pendulum to reach a point

    Homework Statement A 150g mass on a 2.2m long string is pulled 6.6° to one side and released. How long does it take for the pendulum to reach 2.8° on the opposite side Homework Equations I don't know The Attempt at a Solution I don't know where to start. I was thinking using...
  23. A

    LAB: Ballistic Pendulum + Conservation of Momentum

    I'm doing the prelab questions which require conceptual questions, not so much of math. The experiment is a typical ballistic pendulum lab - you'd shoot a paintball twoard a pendulum bob, and you measure the height the pendulum bob reaches after collision to calculate the related velocities...
  24. F

    Coupled pendulum oscillations.

    http://www.google.pt/imgres?q=pendulo+acoplados+resson%C3%A2ncia&um=1&hl=pt-PT&sa=X&biw=1280&bih=656&tbm=isch&tbnid=BSwiWnZmGwlLGM:&imgrefurl=http://www.oficinadaciencia.com/Produtos/Default.aspx%3Fid%3D6493&docid=n05kCljLeoXYCM&imgurl=http://www.oficinadaciencia.com/imgs/ReadImage.aspx%253FpId%2...
  25. P

    Solve Pendulum Swing Angle Problem - Physics Adorers

    Greetings Physics adorers! I was wondering if somebody could please check my work for the problem below. A pendulum with a length 2m has a velocity of 3 m/s at its lowest point. What is the largest angle it creates relative to the horizontal as it swings. Hint: use energy conservation...
  26. C

    Determining Height of Pendulum Attachment Point

    Homework Statement There was this question involving a pendulum expriment: the five values of the square of the period (T^2) was plotted against the 5 values of the distance y in centimetre from the floor to the centre of the bob. I was then asked to determine the intercept on the...
  27. J

    Rotational motion pendulum problem

    Homework Statement Homework Equations ƩF = ma The Attempt at a Solution I know how to break this problem up into the x and y direction Y Direction: Ft cosθ - Fg = 0 X Direction: Ft sinθ - Fg = mv2 / r The hint says to find the inward radial component. I'm guessing this...
  28. G

    Conical pendulum question - I really don't know what to do - ?

    Homework Statement A particle of mass 15g is attached to the end of a string of length 50cm, rotating at 6rads-1 to form a conical pendulum. Find a) The tension in the string Find b) The angle 2. The attempt at a solution Okay I get that Tcosθ= mg & TSinθ=...
  29. TheFerruccio

    What is the velocity of a pendulum when impacted by another mass?

    I'm computing an energy problem whereby a mass is being suspended from a pendulum. I think I have this right, but it would mean that I messed up with an earlier computation. Two masses will impact, and they both hang on wires of 8.5 feet long. When both masses are hanging down, they are 1...
  30. L

    Conical Pendulum, find tension, radial force, speed, period, and angular speed

    Homework Statement A metal sphere is attached to the end of a string and then set in motion such that it rotates in a horizontal circle as shown in the sketch. The metal sphere has a mass of 0.5kg and the radius of the circle is .2m. 1)Find the tension in the string 2)Calculate the radial...
  31. H

    What could T^2 be? Pendulum lab

    Homework Statement I did a physics lab in high school the other week, and I did not look at the rubric for the lab report until now. The lab's purpose was to find the correlation between mass and swing periods, and length and swing periods. The rubric asks to graph T vs. m, T vs. L, and T^2 vs...
  32. B

    Finding the Maximum Height of a Pendulum Swing

    Hello, I have a physics lab tomorrow and have to answer this question to be admitted in. We haven't begun to talk about Pendulums in lecture yet, so I have NO idea where to start. Here's the question: A mass of 40 kg suspended from a 43-cm long light string forms a simple pendulum. The mass...
  33. T

    Optimizing Time for a Ball on a Sloped Path: Arc or Chord?

    Homework Statement We let a ball with mass m to slide down under the influence of his weight the path defined by the chord or the path defined by the arc of the circle until the ball reach the lowest point, as it seems from the picture. In which path the ball will make the shorter time to...
  34. B

    Probability Density Function for a Pendulum?

    What is the probability density equation as a function of angle for a simple pendulum using the small angle approximation? I got 1/(2 pi θmax) sec(sqrt(g/L)t) but it doesn't seem right.
  35. A

    Pendulum like question? hmm

    Homework Statement One end of a cord is fixed and a small 0.310-kg object is attached to the other end, where it swings in a section of a vertical circle of radius 2.50 m as shown in the figure below. When θ = 28.0°, the speed of the object is 9.00 m/s. At this instant, find each of the...
  36. S

    Simple pendulum with friction ODE

    I'm trying to figure out how to find the general solution for a simple pendulum with friction. y'' + ky' + (g/L)y = 0 I know how to find the solution for a simple pendulum without friction: y'' = -(g/L)y ... which leads to ... y = Acos((g/L)x) So far I have: y'' + ky' + (g/L)y =...
  37. T

    MATLAB Plotting Simple Pendulum in MATLAB: Tutorials & Tips

    I'm really confused at the moment and would quite appreciate some guidance. I've got little to no background in Matlab and am needing to plot a simple pendulum. I have found the equation of motion which is q(doubledot) = -(g/l)sin(beta) I don't know how to go about this? After...
  38. M

    Pendulum of unknown length and unknown g, only period given

    Homework Statement Pendulum of unknown length, l, has period of 9.32 seconds. Length is increased by 1 metre, and time period increases to 9.734 seconds. Calculate original length of pendulum and determine whether the experiment was conducted on earth. Hint: g is not assumed to be 9.81 ms^-2...
  39. A

    Why is the Time Period of a Pendulum & SHM Different?

    can someone please tell me why is the time period of a simple pendulum independent of the mass m of the bob while the time period of a simple harmonic oscillator is T=2∏√m/k! pleaseeeee help . Thankyou sooo much :)
  40. K

    Pendulum moving with constant veloctiy

    Homework Statement Consider a pendulum that consists of a mass M hanging from a massless string of length r. The string is being pulled upward at constant velocity through a tiny hole in the ceiling, so the length of the pendulum is given by r = r0 - alpha*t, where alpha is a constant. Let...
  41. O

    What Acceleration Does a Jet Need to Alter a Pendulum's Position?

    Homework Statement A pendulum has a length L = 1.47 m. It hangs straight down in a jet plane at rest, as shown by the dotted line in the figure. Then the jet accelerates uniformly, and during that time, the pendulum moves to the equilibrium position shown by the solid line, with D = 0.39 m...
  42. J

    What is the period of a book swinging like a pendulum?

    1. In the figure below, a book is suspended at one corner so that it can swing like a pendulum parallel to its plane. The edge lengths along the book face are 28 cm and 19 cm. If the angle through which it swings is only a few degrees, what is the period of the motion? 2. I=(ML^2)/12...
  43. A

    Using the formula for a rigid pendulum.

    How to use the formula for a rigid pendulum? Given the formula T = 2π√(2L/3g) (1) how do you change to get T^2 = ? (2) And then how (1) to get g = ? Here's what I've tried, but I'm not sure if they are correct: (1) T^2 = 4π^2 x (2L/3g) (2) g = [4π^2 x (2L/T^2)] ÷ 3 (3) The experiment...
  44. khurram usman

    Time dilation in the period of a pendulum

    i just started studying special theory of relativity and am confused a lot. its first consequence,that is moving clocks run slow confuses me a lot. if two events happen then the time difference between them as measured by a clock in a frame moving at .9c would be lesser than the time measured by...
  45. C

    Pendulum consists of a rod of mass m attached to a light rod

    Homework Statement A pendulum consists of a uniform rod of mass m and length l hanging from the bottom end of a light rod of length l which top end is fixed to the ceiling. (see file attached) System moves in a vertical plane. Find equations of motion. Coordinates of the center of mass...
  46. C

    Find G in Pendulum Experiment: Help Solve I Need

    I Need help...I'm not getting the value of "g" correctly..please someone help/ This is a pendulum experiment to find "g". S L EL T TT T^2 G...
  47. A

    Inertia of a pendulum with disc

    A pendulum consists of a uniform thin rod of mass 5 kg and length 2 m to which is fixed a circular disc of mass 8 kg and radius 0.4 m. There is a pivot at one end. (a) Find the CoM and Moment of Inertia when the disc is: (i) half way along the rod; (ii) at the opposite end of the rod to the...
  48. F

    How do I calculate the mass acting on the cart in a pendulum impacting device?

    I am designing a pendulum impacting device for an experiment. The pendulum will impact a cart on a track. I'd like to calculate theoretical kinetic energy values for the pendulum at the point of impact. The pendulum is made of a hollow aluminum bar, with a steel plate bolted on at the bottom. I...
  49. X

    Momentum of pendulum at its lowest point

    A pendulum of length L swings from rest at a starting angle of θ from the vertical. Assume the mass is concentrated at the end of the pendulum; find its momentum at its lowest point. Please help, thx:)
  50. C

    Double Cart Inverted Pendulum Mechanics

    Homework Statement Consider an inverted pendulum system as described in https://en.wikipedia.org/wiki/Inverted_pendulum. The system consists of a cart with mass M to which a pole of length l and mass m is affixed via a pivot point. Forces applied to the cart move it along a track. At any point...
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