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timekeeper, used in homes and offices for 270 years, and achieved accuracy of about one second per year before it was superseded as a time standard by the quartz clock in the 1930s.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. X

    Acceleration/force questions on Pendulum

    I am trying to replicate worms armageddon's ninja rope physics, it's simply a pendulum. But it has many problems.. I actually know period of a pendulum, angular speed etc.. but I need instantaneous acceleration, speed and how many forces are applied.. It will not be a simply pendulum because...
  2. T

    Conical Pendulum proof of constant frequency

    Homework Statement A pendulum consists of a particle of mass m at the end of a light rigid rod of length l, the other end of the rod being freely attached to a stationary point 0. Let e(t) be a unit vector pointing along the rod, so that the position vector relative to 0 of the...
  3. B

    Very Simple Work/Energy Pendulum Problem

    Homework Statement A 2.0kg bob of a pendulum is held at an angle of 55 degrees from the vertical. When released it reaches a maximum speed of 3.5m/s. What is the length of the pendulum arm? Homework Equations Ek = 1/2mv^2 Ep = mgh The Attempt at a Solution 1/2 * 2 * 3.5 ^ 2 =...
  4. M

    Finding eigenfrequencies of a coupled pendulum

    Homework Statement This problem is from the 1992 GRE. A tube is free to slide on a frictionless wire. On each end of the tube is attached a pendulum. The mass of the tube is M. The length and mass of the pendula are l and m, respectively. Homework Equations It is given that one of the...
  5. H

    Forces of inverted pendulum

    Homework Statement I am trying to understand where the forces in the inverted pendulum comes from starting with this horizontal force equation: http://www.engin.umich.edu/group/ctm/examples/pend/inveq2.GIF It is associated with this picture...
  6. Z

    Exploring the Ideal Pendulum: A Mathematical Analysis of Torque

    Can the ideal pendulum, i.e. massless string etc., be explained using torque?
  7. T

    A pendulum on some moon has a length of 1.5meters and a period of

    A pendulum on some moon has a length of 1.5meters and a period of 4.2seconds. On Earth a girl throws a rock 13meters in the air, if she was on that moon how high would that same rock go if she threw it with the same effect? (Ignore all air resistance)
  8. S

    Galileo's pendulum could show that time is relative

    Galileo's pendulum could have shown that local time is relative Making experiments with pendulums Galileo discovered the following properties: - Pendulums nearly return to their release heights. - All pendulums eventually come to rest with the lighter ones coming to rest faster. -...
  9. A

    Expression for time period of simple pendulum

    Which of the two is a better expression for the time period of a simple pendulum? t-=2∏\sqrt{(l/g)} or t=2∏\sqrt{(1/T/m)} ; l=length of the pendulum T=time period of the pendulum m=mass of bob...
  10. G

    Finding the period of a simple pendulum given angular acceleration

    Homework Statement A physical pendulum oscillates through small angles about the vertical with the angle, measured in radians, obeying the differential equation d2θ/dt2 = -4πθ. What is the period of the oscillation? Homework Equations T = 2π √(L/g) The Attempt at a Solution I...
  11. S

    Pendulum Amplitude and phase constant

    Homework Statement A simple pendulum of length 1m with bob mass 125g is pulled 15 degrees to the right and released at t=0.What are the phase constant and amplitude? Homework Equations θ(t)=Acos(ζt+phi) ---> my teacher gave us a weird symbol that I've never seen before, it has always...
  12. K

    Pendulum Problem: Calculate Initial Speed of Actor

    Homework Statement [/b] An actor of mass 65.0 kg wishes to make a grand entrance onto a stage during a play. He attaches himself to a cable having length R=5.00 m. A stagehand gives the actor a push, imparting an initial speed onto the actor at heigh 1.5 m above the lowpoint of his ensuing...
  13. M

    Pendulum on a spring accelerating upward

    Homework Statement A pendulum on Earth consists of a mass m suspended on a massless spring with equilibrium length d and spring constant k. The pendulum point of support is moving up with constant acceleration a. What is the Hamiltonian of the system? Derive the Hamiltonian equations...
  14. J

    Circular motion/conical pendulum?

    one end of a light inelastic string is attached to a point A vertically above a point O on a smooth horizontal plane and at a height h above it. The string carries a particle P of mass m at its other end. WHEN JUST TAUT the string is inclined to the vertical at an angle S if P moves in a...
  15. M

    Using a pendulum to find the distance to the sun

    Hello, One or two years ago I had a mathematics lecture where one part of it was using basic formulae, a pendulum and the distance to the centre of the Earth to find out what the distance to the sun was. Recently, I came across a question which asked me to figure out the distance to the...
  16. J

    What is the Frequency of Small Amplitude Oscillations in an Inverted Pendulum?

    Homework Statement A pendulum consists of a massless rigid rod with a mass at one end. The other end is pivoted on a frictionless pivot so that it can turn through a complete circle. The pendulum is inverted, so the mass is directly above the pivot point, and then released. The speed of the...
  17. C

    What is the maximum speed of the pendulum?

    Homework Statement A simple pendulum with mass m = 1.7 kg and length L = 2.42 m hangs from the ceiling. It is pulled back to an small angle of θ = 8.6° from the vertical and released at t = 0. Qn: What is the maximum speed of the pendulum? Homework Equations θ=θmax*cos(ωt+∅) The...
  18. R

    Period of a Simple Pendulum with Varying Masses and Gravitational Forces

    Homework Statement The usual formula for the period T of a simple pendulum of length l is T=2\pi\sqrt{\frac{l}{g}} where g is the acceleration due to gravity. Denoting rhe inertial mass of the pendulum bob by m_{i} and its gravitational mass by m_{g}, derive an alternative expression for T in...
  19. N

    [ Spring pendulum ] Centrifugal Force transmissibility

    Hey folks, I just wonder how you guys think about this. Assume that there is a spring pendulum rotating at hinge (Free swing or forced swing). In this case, can I calculate force transmissibility (transmitted force amplitude to ground via spring devided by centrifugal force amplitude) ...
  20. N

    Period of arbitrary amplitude pendulum using average speed

    Homework Statement A simple pendulum of length L is pulled aside to angle θm then released from rest. For arbitrary angle θ on the path of motion the acceleration along the path is -gSinθ. The speed at this point is V(θ)= √[2gL (cos θ - cos θm)]. Find the period T of the pendulum (do not...
  21. E

    Pendulum & Partition Function Problem

    [b]1. A pendulum of mass m hangs from a weightless string of length l The string makes an angle θ with the vertical Find (i) <θ> (ii) <θ^2> (iii) <v> (iiii) <v^2> Homework Equations The Hamiltonian in terms of θ and the angular momentum L= H= L^2/2ml^2 + mgl(1-cosθ) The...
  22. V

    I dont know how to graph these pendulum things

    Homework Statement with frequency as the dependent variable, plot graphs of frequency versus (i)Amplitude, for a length of cm and a constant mass (ii)mass, for a length of 100cm and constant amplitude (iii)length, for a constant amplitude and constant mass. Homework Equations i think i got one...
  23. K

    Measuring Impact Velocity with a Ballistic Pendulum Prototype

    some device or contraption to measure point impact velocity - ballistic pendulum ? i hope you guys and gals can point me in the right direction for a prototype i am working on. I am looking for a device that measures impact velocity. much like a ballistic pendulum only much sturdier than the...
  24. Q

    Discovering G: Calculating Torsion Constant with Torsion Pendulum Experiment

    Homework Statement i did my experiment on torsion pendulum and there is a graph that i am supposed to draw ( C as a function of 1/L) where C is the tosion constant and L the length of the wire after that they give me a formula C=1/32L *∏*G*a^4 where G is called the modulus of rigidity and a...
  25. Q

    Torsional Pendulum: History, Uses & Applications | Learn More

    i just want like 3 to 4 lines about the history of torsional pendulum like who started with it and what is it used for?? please quick reply
  26. F

    Mathematica Mathematica: Differential equations for double pendulum

    Hello Im new here, I hope I'm not disturbing anyone. Following this guide below, I am trying to find two 2. order differential equations, one for q1'' and one for q2'', describing the movement of the double pendulum. I have no problems with the mathematics, but when the guide tells me to...
  27. O

    Bullet pendulum problem w/ Calculus - AP Physics C

    Homework Statement See problem here: http://i184.photobucket.com/albums/x153/spl10246/problem.png Solution: http://i184.photobucket.com/albums/x153/spl10246/solution1.png http://i184.photobucket.com/albums/x153/spl10246/solution2.png Homework Equations p = m * v K = .5 * m *...
  28. C

    Determine the length of a pendulum on the moon

    So I'm working on homework, and encountered this problem. I thought I understood what to do, but I'm not getting the right answer. I'm so frustrated I decided to create an account, so this is my first post. I'll do my best to adhere to the PF format of questions. The Question is: A pendulum...
  29. R

    Pendulum swinging above earth's surface

    Homework Statement Assume all oscillators are frictionless. a) A pendulum consists of point mass Mo swinging on a massless string of length Lo, with period To = 9.42 s on the surface of the Earth (at RE, the radius of the Earth). Find T1, the period of the same pendulum if it swings on a...
  30. L

    Finding the Velocity of the Bob on a Pendulum

    Homework Statement A 2.0 m pendulum is released from rest when the support string is at an angle of 25 degrees with the vertical. What is the speed of the bob at the bottom of the string? Homework Equations KE=1/2mv^2 PE=mgh The Attempt at a Solution I thought that height would...
  31. J

    Speed of Pendulum Bob at Lowest Point

    Homework Statement A simple pendulum consists of a bob of mass 1.8kg attached to a string of length 2.3m. The pendulum is held at an angle of 30° from the vertical by a light horizontal string attached to a wall. If the horizontal string is cut close to the bob and the pendulum swings down...
  32. H

    The physical pendulum - distance, period, and angular frequency

    Homework Statement The physical pendulum shown on your paper is a 27.0 kg wedge of a circular disk of uniform density with radius, R=1.87 m and opening angle β=0.847 radians. The pivot point of the pendulum can be moved along the center line of the wedge as shown on your paper...
  33. M

    Period of a Pendulum | Calculate in 1.2s

    I am getting confused regarding what a 'period' in a pendulum is. In a recent Olympiad/Exam I was given this question... Can you please give me the method in which it can be done so that I can solve these type of questions with ease if they appear in future... Thanks :smile: A Pendulum...
  34. A

    What is the connection between simple harmonic motion and pendulum motion?

    Homework Statement What is the connection between simple harmonic motion and pendulum motion? Homework Equations Harmonic motion period=T=2piroot(m/k) Pendulum motion period=T=2piroot(L/g) The Attempt at a Solution Conservation of momentum?? Thanks for any help!
  35. A

    Length of Pendulum: Does COM Matter?

    Homework Statement Does it matter whether you measure the length of the pendulum to the center of mass of the ball or to the bottom of the ball Homework Equations T=2pi*root(L/g) The Attempt at a Solution I can see that L (length) is a factor, but I'm not sure why it matters...
  36. S

    Inelastic collision - pendulum

    Alright, I did all the work for this problem, but do not know the correct answers and therefore cannot check my work with 100% confidence. So if somebody could look it over and let me know if I did everything correctly or not, I'd appreciate it. The answer I calculated for part e seemed kind of...
  37. J

    Rotating pendulum hang from a wooden bar with a revolution speed of 0.15 rev/s.

    Homework Statement Part c: A pendulum is attached to a 0.15m wooden bar sticked horizontally to a table by a string of 0.12m. If the system is revolved with a revolution speed of 1.5 rev per second, what is the angle θ the pendulum make with respect to the vertical axis? Homework...
  38. J

    A pendulum of length 'L' having a mass 'M' attached as it's bob and it

    a pendulum of length 'L' having a mass 'M' attached as it's bob and it oscillates with a time period 'T'. what will be the force tangential to the pendulum 1. just above the point of suspension of the pendulum 2. at a distance 'r' below the point of suspension
  39. W

    Simple harmonic motion of a pendulum

    Homework Statement I need to find the phase difference between two pendulums. My problem is that I don;t seem to have enough information to calculate the phase for the second pendulum (I have already calculated the phase for the first). The pendulum is 0.35m long, and is at 0.00rad at...
  40. M

    Swinging Pendulum hits Block on Table- Find Distance and Acceleration?

    Homework Statement A 1.00 kg pendulum hanging from a length 1.50 m starts horizontal to the ceiling and swings (until it's perpendicular to the ceiling) to hit a 4.00 kg block. The coefficient of friction is .30. a) What distance does the block travel? b) Assuming there is no friction...
  41. P

    Calculating 'g' with Slope of Pendulum Graph

    Homework Statement Using the slope from a graph of the square root of the pendulum's length vs period (which would be a linear relationship), calculate the experimental acceleration due to gravity. Homework Equations I'm trying to figure out what equation I can use to solve for 'g'...
  42. X

    I with finding moment of inertia for pendulum

    Homework Statement A grandfather clock uses a physical pendulum to keep time. The pendulum consists of a uniform thin rod of mass M and length L that is pivoted freely about one end, with a solid sphere of the same mass, M, and a radius of L/2 centered about the free end of the rod. Obtain...
  43. I

    Pendulum - equipartition experiment

    Homework Statement The problem is : http://i44.tinypic.com/2v7yo29.png Homework Equations The Attempt at a Solution For part a ) I have stated that: The total energy is equivalent to the conservation of energy i.e the two expressions obey the conservation principle. The expression dealing...
  44. QuarkCharmer

    How Does Graphing Time Squared Reveal Pendulum Dynamics?

    Homework Statement We did a lab, where, in the first part we timed the period of a pendulum with varying lengths. In the second part, we timed the period of a pendulum with varying masses. I got the results that I expected to get. However, I do not understand two of the lab questions...
  45. C

    Calculating the Acceleration of a Simple Pendulum

    Homework Statement A simple pendulum has a length of 4.9 m and is pulled a distance y = 0.5 m to one side and then released. (a) What is the speed of the pendulum when it passes through the lowest point on its trajectory? (b) What is its acceleration when it passes through the lowest...
  46. X

    How Long Does It Take for a Child to Swing Back and Forth on a Tire Swing?

    Homework Statement A horizontal tree branch is directly above another horizontal tree branch. The elevation of the higher branch is 9.45 m above the ground, and the elevation of the lower branch is 5.58 m above the ground. Some children decide to use the two branches to hold a tire swing...
  47. X

    Lagrangian of a Pendulum on a rotating circle

    Homework Statement Find the Lagrangian of a simple pendulum of mass m whose point of support moves uniformly on a vertical circle with constant angular velocity. (So basically there is a circle around the origin that spins with a constant angular velocity and the pendulum is attached to the...
  48. QuarkCharmer

    Ballistic Pendulum results.

    Homework Statement I was just wondering if someone would be kind enough to look over these solutions and tell me if I am correct. The lab was a simple ballistic pendulum, which I am sure every physics student performs. Homework Equations The Attempt at a Solution 1.)...
  49. Q

    Experiment: Pendulum with Spring - Simulate Oscillation Trajectory

    Hello everybody :) I need some help in an experiment simulation :) If you will make a pendulum with a spring instead of a string or rope (nonelastic), then bend it over on θ angle and then let it go - it will start to oscillate around with different manner than a simple pendulum :) with...
  50. C

    Finding Linear Graph for Pendulum Dilemma Equation

    Homework Statement I am suppose to find a linear graph for the equation T=2pie(√L/√g) Homework Equations The Attempt at a Solution The best linear graph I could think of was L/T^2. Am I doing it right? Thanks.
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