Pulley Definition and 1000 Threads

A pulley is a wheel on an axle or shaft that is designed to support movement and change of direction of a taut cable or belt, or transfer of power between the shaft and cable or belt. In the case of a pulley supported by a frame or shell that does not transfer power to a shaft, but is used to guide the cable or exert a force, the supporting shell is called a block, and the pulley may be called a sheave.
A pulley may have a groove or grooves between flanges around its circumference to locate the cable or belt. The drive element of a pulley system can be a rope, cable, belt, or chain.
The earliest evidence of pulleys dates back to Ancient Egypt in the Twelfth Dynasty (1991-1802 BCE) and Mesopotamia in the early 2nd millennium BCE. In Roman Egypt, Hero of Alexandria (c. 10-70 CE) identified the pulley as one of six simple machines used to lift weights. Pulleys are assembled to form a block and tackle in order to provide mechanical advantage to apply large forces. Pulleys are also assembled as part of belt and chain drives in order to transmit power from one rotating shaft to another. Plutarch's Parallel Lives recounts a scene where Archimedes proved the effectiveness of compound pulleys and the block-and-tackle system by using one to pull a fully laden ship towards him as if it was gliding through water.

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  1. jasonpeng

    Why Is Tension Equal in a Frictionless and Massless Pulley System?

    I've got a problem with understanding the pulley system. In a basic pulley, if the force pulling M upwards is T, and the force pulling m upwards is also T, why is it that T is equal for both m & M? For some reason I feel inclined to believe that the T pulling m upwards is equal to the weight of...
  2. M

    Torque to rotate pulley with equal mass on each side.

    Lets say there is a pulley attached to the ceiling. Hanging on the pulley is a rope and on each end is a 1000 lb. weight. I believe that theoretically it wouldn't take any torque at all to rotate the pulley if it were frictionless (maybe inertia would play a role, but let's ignore that)...
  3. person123

    Exploring Pulley System Equilibrium: Solving for y when x Changes

    I was working on a pulley system as shown here: The mass on the right and left side is equivalent, and I am solving for when the system is in static equilibrium. Theta is the angle between the rope on either side of one of the pulleys. H and y are both measured from the original position of...
  4. Bunny-chan

    Conservation of the string length in pulleys

    Homework Statement This is a common massless string and pulleys problem. I'd just like to understand why, according to the solution, l_2 + 2l_1 = constant. It doesn't seem to me that two times the l_1 length is equivalent to l_2. Can somebody explain? Homework EquationsThe Attempt at a Solution
  5. B

    Pulley System on a Big Block: Solving for Acceleration with Zero Applied Force

    Homework Statement Find the accelaration of ##M_1## in the given system if ##F = 0##. Homework EquationsThe Attempt at a Solution [/B] ##x_3 -x_1 = k \iff \ddot x_3 = \ddot x_1## and ##h - y_3 + x_3 - x_2 = l \iff \ddot y_3 + \ddot x_2 = \ddot x_3 \qquad (*)## h is the height of block...
  6. S

    Kinetics of System Particle/ Pulley system with masses and i

    I can't seem to solve it, considering inertia can someone please solve it, both of the following question in the given picture. I would be very much thankful.
  7. D

    Calculating Pulley Size for Band Saw Motor

    0 / 0 Hi all I am trying to find the diameter for a pulley on a drive motor for a band saw the motor turns 2800 rpm the next pulley is 11 1/2" away that is 5" dia on the same shaft is the band saw wheel which is 10" dia and must turn 900 rpm . any help would be great. Doug.
  8. K

    Natural frequency of pulley system

    Homework Statement https://www.physicsforums.com/attachments/197474 Homework Equations 3. The Attempt at a Solution [/B] ma + kx = 0 I know how to do it if the spring is in the middle of the pulley, not using energy method. by the free body diagram. But I am stuck at this. [Updated: I know...
  9. Alok

    How pulley diameter affects forces?

    Whether the diameter/radius of pulley affects the force required in lifting a weight?
  10. W

    Kinematics Belt and Pulley Problem

    Homework Statement I think I made a mistake somewhere.. Homework Equations T = Jα T = F*R The Attempt at a Solution A) I started with T = Jα Since there is no slip, αm = αL Thus: Tm / Jm = TL / JL Plugging in, we find TL = Tm * JL / Jm = 2560 Now use T = F*R. Tm = Fm * Rm Plugging in...
  11. R

    Boatswans Chair pulley Question

    Homework Statement The question has been screenshotted, along with the given diagram. Basic stuff I know, but I can't seem to get my head around pulley systems. T Homework Equations F(net) = m ⋅ a(system) The Attempt at a Solution I understand the rope to be considered inextensible. Also...
  12. danielhep

    Mastering Physics: Acceleration of a Pulley

    Homework Statement A string is wrapped around a uniform solid cylinder of radius r, as shown in (Figure 1) . The cylinder can rotate freely about its axis. The loose end of the string is attached to a block. The block and cylinder each have mass m. Find the magnitude α of the angular...
  13. U

    Force on a Pulley: Understanding Tension and Tangents

    Homework Statement I'm having trouble understanding an example given in K&K's Intro to Mechanics textbook. 'A string with tension ##T## is deflected through an angle ##\theta_0## by a smooth fixed pulley. What is the force on the pulley'. I don't understand how (in the first picture) they...
  14. jerryd87

    Three weights and two pulley system

    Homework Statement The goal is to find the tension in the strings and acceleration of each block. M1=8 kg, m2=1 kg, and m3= 2 kg. This is a study problem so not really homework but I am having trouble finding anything quite like this problem. Homework Equations m1g-t1=m1a1 t2-m2g=m2a2...
  15. S

    Atwood with Sliding mass and real pulley

    Homework Statement Block 1 with mass m1=4.04 kg rests on a very low friction horizontal ledge. This block is attached to a string that passes over a pulley, and the other end of the string is attached to the hanging block 2 of mass m2=2.02 kg, as shown. The pulley is a uniform disk of radius...
  16. R

    Time period of a block hanging from a pulley

    Homework Statement :[/B] The figure shows a pulley block system in equilibrium. If the block is displaced down slightly from its position and released, find the time period of the oscillation. Assume friction is sufficient. I: moment of inertia of pulley k: spring constant R: Radius of pulley...
  17. E

    Chain Sliding on a Pulley: Acceleration and Force Analysis

    Homework Statement On a pulley with a very small radius and negligible inertia, that rotates without friction around its fixed horizontal axis, there is a chain of mass m and length l. The chain starts sliding from its equilibrium position. Let x be the distance between the ends of the chain...
  18. C

    Find acceleration of a pulley system

    Homework Statement A pulley of radius, R and moment of inertia, I=2MR^2 is mounted on an axle with negligible friction. Block A, with a mass M, and Block B, with a mass of 3M, are attached to a light string that passes over the pulley. Assuming that the string doesn't slip on the pulley, Answer...
  19. L

    Why Ignore Tension In Pulley and Work Energy Problems?

    A pulley and block system is a favorite type of system for analysis when considering work-energy problems in beginning dynamics. It's commonly recommended that the best approach to the system is to write an equation for the whole system, while ignoring the work done by cables/ropes and focusing...
  20. S

    Person pulling themselves up a double pulley

    Homework Statement A man is pulling himself up to a pulley that consists of two disks welded together as shown(same center). The man is currently pulling straight down on the rope in his hands with a force of magnitude 447.2 N (on the bigger disk). The other rope is also vertical and is...
  21. H

    Angular acceleration of an atwood pulley

    Homework Statement An Atwood machine is a rope that passes over a pulley with a block attached to each end of the rope so that the blocks are not in contact with the floor. The frictionless axle of the pulley is oriented horizontally, and the rope is vertical save where it makes contact with...
  22. Guidestone

    Why Does Pulley and Spring Setup Result in 2(x1+x2) Displacement?

    Hey guys, I'm wondering why the displacement of the mass mounted in this setup is 2(x1+x2)?. I'm assuming that when the pulley rotates(when the mass is pulled downwards) the distance between the initial point and the end point of its center and the distance traveled by the mass are equal...
  23. physicsdude101

    A pulley of mass m using conservation of energy

    Homework Statement Consider a massive pulley of mass m and radius r shown in the figure below, with two objects hanging off it having masses m and 2m, respectively. The pulley can be considered as a uniform disk, and the string is massless, does not stretch and does not slip. By considering...
  24. S

    Pulley system and energy conservation?

    Homework Statement [/B] Two blocks are connected by a string that passes over a massless, frictionless pulley, as shown in the figure. Block A, with a mass mA = 4.00 kg, rests on a ramp measuring 3.0 m vertically and 4.0 m horizontally. Block B hangs vertically below the pulley. Note that you...
  25. J

    Newton's Second Law -- Accelerations in a pulley system

    Homework Statement A 20-kg block with a pulley attached slides along a frictionless ledge. It is connected by a massless string to a 5.0-kg block via the arrangement shown in Figure. (a) draw complete free body diagrams for the masses and Find (b) the acceleration of each block and (c) the...
  26. anony123

    Why does adding more pulleys increase the force on a block?

    Hello, First of all, I'm new to this forum and to not know whether this thread is in the right place or not. If not, feel free to replace it. I'm in my first year of university, studying industrial engineering. On a test I got the following image: The red square is a block with a specific...
  27. DaniV

    Finding Angular Velocity of Pulley with Rope and Mass

    1. Homework Statement a circular homogenic pulley (disk) with radius R and mass of M hanging on a axis that passes through his center, the pulley rotating without friction. we wrap the pulley with a rope with a total mass of mr and length of L and in the other side of the rope we ataching...
  28. J

    "How Fr=Ialpha Works in a Pulley w/ Mass

    Homework Statement How does Fr=Ialpha work and how is it applied to a pulley with one mass attatched? Homework Equations F * r = I * alpha I = moment of inertia The Attempt at a Solution I'm assuming F would be the tension of the pulley with the string. But how does that equation work? can...
  29. A

    Calculating the force for a differential pulley

    Homework Statement A differential pulley carries a weight W. The chain used has N links per foot. The bigger pulley has n notches, which can hold two chain links each. The smaller pulley contains n - 1 notches, which can also hold 2 chain links. The friction is such that the ratio of the force...
  30. A

    What is the Normal Force on an Incline Plane with Two Connected Blocks?

    Homework Statement On an incline plane of known angle α (30°) lies a block of mass m1 (0.23 grams), connected through a pulley without friction to a second block of mass m2 (0.18 grams). Determine: - The acceleration of the block - The Tension force - The Normal force of the plane Homework...
  31. soolights

    Solving a Tricky Physics Pulley Problem: Finding M2 with Tension and Mass M1

    <Mentor's note: moved from a technical section, therefore no template> hey guys, i have a question about a tricky physics 1 problem our teacher gave us today, paraphrased as follows: there is a mass M1 on a flat, frictionless horizontal table connected to a pulley, and on the other side of the...
  32. H

    Falling Mass on a Pulley - Rotational Energy

    Homework Statement A frictionless pulley has the shape of a uniform solid disk of mass 2.50 kg and radius of .2 m. A 1.50 kg mass is attached to a very light wire that is wrapped around the rim of the pulley, and the system is released from rest. a) How far must the stone fall so that the...
  33. R

    Solving for Velocity on a Pulley System

    Homework Statement In the picture below. Homework Equations Velocity on a pulley = (velocity on left rope + velocity right rope)/2 Pulley A and C have 0 velocity. The Attempt at a Solution By inspection the right sided rope on pulley A is 120 mm/s going up. After that is when I get confused...
  34. R

    Finding Tensions and Accelerations with Moveable Pulley

    (Moved to the homework section by moderator.) Please see the image. My confusion is with a moveable pulley. Can I just do my balances on both 1kg and 2kg masses disregarding the acceleration of the pulley? Here are my eqns. Object numbers 1, 2 and 3 denote the 3kg, 1kg and 2 kg weights. 4 is...
  35. ikihi

    How Do You Calculate the Angular Motion of a Pulley System?

    Homework Statement Consider a pulley with a mass-less cord attached to its edge. The rope hangs a distance of d= 2.50 m below the bottom of the pulley. Attached to the end of this cord is a block with mass 3.00 kg. There is also an electric motor attached to the pulley which supplies a torque...
  36. KentVibEngineer

    Pulley rotational speed in block and tackle

    Homework Statement For the pictured block and tackle system, formulate an equation to solve for the rotational speed of each sheave wheel for a given line pull speed. (ignore friction, slippage, line stretch) (Mass, force, efficiency, mechanical advantage are not the focus of this. Pulley...
  37. ikihi

    Mass and pulley system (Rotational Dynamics)

    Homework Statement Consider a pulley with a mass-less cord attached to its edge. The rope hangs a distance of d= 2.50 m below the bottom of the pulley. Attached to the end of this cord is a block with mass 3.00 kg. There is also an electric motor attached to the pulley which supplies a torque...
  38. T

    Finding pulley diameter with speed in rpm

    Homework Statement [/B] In a pulley system, pulley A is moving at 1,500 rpm and has a diameter of 15 in. Three pulleys, B, C, and D, all of different sizes, are attached to a single output axle. Speed and torque output are changed within the system by moving the drive belt between pulleys B...
  39. J

    Worker Sim Pulma Sheen: Solving a Pulley Problem

    Repost since it was removed from double questions. 1. Homework Statement Worker Sim Pulma Sheen uses a system of pulleys to lift a 5000 N box 2 meters while pulling on the rope with a force of 500 N. This means the worker had to pull how much rope from the pulley system? a) 0.2m. b) 2m c) 5m...
  40. T

    Work problem - Rope, pulley and brick (applied integration)

    If a brick is pulled across the floor by a rope thruogh a pulley, 1 meter above the ground - and work = W, where W = 10N , (in Newton).Show that the horizontal component of W, which is pulling the brick has the size \frac{10x}{\sqrt{1+x^2}} (*) Use this to calculate the amount of work needed...
  41. S

    Acceleration of a Mass in a Pulley System

    The block 1 of m1 sheets of mass on an inclined plane without friction at an angle θ to the horizontal. One end of a non-extendable rope with no mass is attached to lock 1. The chain is wound around a non-frictionally mobile pulley P of negligible mass and is also connected to the wall at the...
  42. Z

    Determine the force in a pulley system

    Homework Statement If A has a mass of 300kg, determine the mass of B if the system in figure P4-28 is to be in balance. (What I couldn't understand is the 2Tb in the answer.) Homework Equations ΣFy=0[/B]The Attempt at a Solution Since the pulley on top is connected with two pulley at the...
  43. Elvis 123456789

    Lagrangian of two masses connected by a pulley on inclined p

    Homework Statement Two masses, m1 and m2, are attached by a light string of length D. Mass m1 starts at rest on an inclined plane and mass m2 hangs as shown. The pulley is frictionless but has a moment of inertia I and radius R. Find the Lagrangian of the system and determine the acceleration...
  44. Shashank Holla

    Acceleration due to *equal* weights on pulley system

    Homework Statement [/B] Which of the following is correct? 1. The acceleration of pulley B is g/11 downwards 2. The acc. of pulley C is g/11 upwards 3. Tension in string passing over pulley A is 12.46g N 4. Tension in string passing over pulley A is 10g N Homework Equations F=m.a[/B]The...
  45. C

    How Do You Solve a Complex Energy Pulley Problem?

    1. The mb = 25 kg block is 2 m above the ledge. The pulley is a uniform disk with a radius of 10 cm and mass m = 4 kg. 2. (a) Find the speed of the 25 kg block just before it hits the ledge. (b) Find the angular speed of the pulley at that time. (c) Find the tensions in the strings. (d) Find...
  46. J

    Two Blocks and a Pulley Friction Problem

    Homework Statement System comprised blocks, a light frictionless pulley and connecting ropes (see diagram). The 9.0kg block is on a perfectly smooth horizontal table. The surfaces of the 12kg block are rough, with μk = .2 between the two blocks. If the 5.0 kg block accelerates downward when it...
  47. J

    How Does a Speck of Dust Affect the Motion of a Box on an Inclined Ramp?

    Homework Statement 100 kg box is held in place on a ramp that rises at 30° above the horizontal. There is a massless rope joint to the box that makes a 22° angle above the surface of the ramp. Coefficients of friction between the box and the surface of the ramp are μk = 0.40 and μs = .60. The...
  48. M

    What is the Time to Pivot the Rod with a Spinning Disk?

    Homework Statement A rod of length L = 20 m and mass m = 50 kg juts out perpendicular to a wall. The rod is designed to pivot vertically about the point where it intersects the wall. A massless pulley is affixed to the wall a height h = 10 m above the rod. A cable is attached to the rod a...
  49. W

    Conservation of Momentum: Pulley System

    Homework Statement Block A (of mass MA) rests on a frictionless horizontal table. It is connected via a light string to block B (of mass MB) hanging over the edge of the table. The pulley itself, a solid disc, has non-negligible mass MC. The light string does not slip over the pulley. What is...
  50. D

    How Is Angular Speed Calculated for a Pulley System?

    Homework Statement Homework Equations v=rω conservation of energy The Attempt at a Solution I don't know whether it is correct or not, and I am quite confused in part b it asks the angular speed of the pulley can I say that v=rω since the pulley and box A,B have a common velocity? so is ω...
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