What is Pulley: Definition and 1000 Discussions

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.

View More On Wikipedia.org
Recent contents Top users
  1. T

    Why Does a Pulley System Double the Upward Force on a Chair?

    Homework Statement http://i.imgur.com/rjxR2.jpg Homework Equations F = ma The Attempt at a Solution I know that the rope is pulling the man up twice as much because there are two points of contact between him and the rope. I'm really just looking for somebody to explain why that...
  2. M

    Solving a pulley system (Dynamics)

    Solving a problem about a pulley system (dynamics) A 100 kg crate is supported by a rope which passes over a 25 kg pulley. A 2nd rope connects the pulley to the ceiling. The system is stationary. ƩFx=0 ƩFy=0 I am having problems setting up the free body diagram to start the problem!
  3. N

    What are common problems encountered when using a double pulley system?

    Homework Statement https://docs.google.com/file/d/0B65UbG8T0LS9SEFRTHhHZmR2NDA/edit Question 2 Homework Equations The Attempt at a Solution Well I tried to draw a diagram but I don't really know where to start tbh, I also can't my head around how 1200N of force only provides 600N...
  4. N

    Quick look over friction pulley system

    Homework Statement Objects with masses m1 = 12.0 kg and m2 = 4.00 kg are connected by a light string that passes over a frictionless pulley. If, when the system starts from rest, m2 falls 1.00 m in 1.70 s, determine the coefficient of kinetic friction between m1 and the table...
  5. C

    What creates the angular acceleration in a pulley?

    Looking at the free body diagram of a fixed pulley with a rope going over the top half, the diagram would show tension going downward on either side and an anchor going up equaling twice the tension. I understand this is this case so the pulley doesn't move in any rectilinear motion. However...
  6. M

    Pulley, Motor and Weight Torque Problem

    Pulley and Motor - Torque Problem Homework Statement When the motor in the figure below lowers the m = 1140kg mass, it produces a tension of 1.04E+4N in the cable on the right side of the pulley. The pulley has a moment of inertia of 79.7kgm^2 and a radius of 0.741m. The cable rides over the...
  7. T

    Newton's second law 3 pulley problem.

    There is no friction and the strings are massless. Find Tension and acceleration. 3. The Attempt at a Solution 1. +T-m1g = m1a 2. m2g-2t= m2a 3. +T - m3g =m3a 4. 2a2 = a1+a3 g(-m1+m2-m3) + 2a2 = (m1 + m2 + m3)a + a1 + a2 -29.4 + 2a2 =11a +a1+ a2
  8. D

    Finding coeficient of friction with a slope/blocks/a pulley

    Homework Statement Two blocks are connected by a thin inextensible string over a frictionless massless pulley as shown on the picture below The acceleration of gravity is 9.8 m/s Given that the two blocks move at 5.7 m/s under an acceleration of 4 m/s^2 calculate the coefficient µk of kinetic...
  9. C

    What is the acceleration of the mass 4m?

    Homework Statement Consider the following system: A mass 4m is suspended with a massless string from a massless pulley wheel. On the other end of the string is another massless pulley wheel with a mass 3m suspended from a massless string on it, and a mass m suspended on the other side...
  10. M

    Dynamics question about boy pulling himself up via pulley

    Homework Statement A 45 kg boy stands on 30 kg platform suspended by a rope passing over a stationary pulley that is free to rotate. The other end of the rope is held by the boy. The masses of the rope and pulley are negligible. Ignore the friction in the pulley. a) If the rope and the...
  11. D

    Masses connected by a pulley on a frictionless surface

    Homework Statement A block of mass 2.6 kg (M1) lies on a frictionless surface. Its connected by a massless pulley and string hanging over the edge of the surface of 3.17 kg (M2). Calculate the acceleration of M1(part 1). calculate the tension in the cord(part 2). the cord is...
  12. R

    Two Blocks Connected by a Massless String Over a Pulley

    A 6.0kg box is on a frictionless 35° slope and is connected via a massless string over a massless, frictionless pulley to a hanging 2.0kg weight. What is the tension in the string if the 6.0kg box is held in place, so that it cannot move? m1= 6.0kg m2= 2.0kg θ=35° So, for Box 1 to be...
  13. S

    Mechanic about wood block, friction and pulley

    Homework Statement Two objects A and B weighing 50 N and 80 N respectively were connected by a light string over a fixed pulley. A was put on a reasonably long and horizontal table surface. The coefficient of sliding friction between A and the table surface is μ = 0.3 while the friction...
  14. J

    Pulley, friction, acceleration

    Homework Statement http://imageshack.us/a/img703/7864/physicsb.png From the image above: a) If there is no friction between A and surface, what is the blocks' acceleration? b) With coefficient of 0.2?
  15. Saitama

    How does the tension in a pulley system change with different masses?

    Homework Statement In the arrangement shown in Fig. 1.18(see attachment) the mass of ball 1 is η=1.8 times as great as that of rod 2. The length of the latter is l = 100 cm. The masses of the pulleys and the threads, as well as the friction, are negligible. The ball is set on the same level as...
  16. M

    Solving Pulley Systems with Multiple Masses and Angles

    Homework Statement A crate is pulled up using frictionless pulleys in the manner shown in the figure. The angle is 45 degrees. The masses are, for the small pulley, m1=3.5 kg, for the traveling pulley, M2=6.5 kg, and for the crate, MC=44.2 kg. What is the minimum tension with which the...
  17. P

    Finding the acceleration of a pulley system

    1. A pulley system consists of Mass A (400g) on a wooden ramp being pulled by Mass B (300g) which is suspended in the air. The board is placed on a table at an angle of 12 degrees. The following values are for the system: Hypotenuse(Length of board): 50cm, Height from table to board (a from...
  18. H

    What is the minimum length for x to lift the bucket 9 meters in 4 seconds?

    http://imgur.com/NMu80 http://imgur.com/NMu80 Hello! I have a problem to solve and I am not quite sure how to. In the linked image i have the values of G, F and D given. F stays constant and right angled towards the lever. The bucket needs to go up 9 meters in 4 seconds. What is the...
  19. H

    Torque on a pulley with a mass

    If there is a load of say, mass =m Kg which is being raised on the end of a light inextensible rope by means of a winch. see attachment. the pulley of the winch has a radium x meters and is let's say that it is frictionless. the acceleration of the load is a ms^-2 can someone tell me...
  20. A

    How Does a Frictionless Pulley System Affect the Force on a Ceiling Hook?

    Homework Statement Two weights are connected--Weight 1 (75.0N) and Weight 2 (125.0N)--by a very light flexible cord that passes over a 70.0N-frictionless pulley of radius 0.400m. The pulley is a solid uniform disk and is supported by a hook connected to the ceiling. I calculated the mass of...
  21. D

    How can I solve for time in a pulley and ramp problem without a given variable?

    Homework Statement A mass m{1} = 5kg is on a frictionless ramp and connected to a cable that passes over a pulley which is then attached to a second hanging mass, m{2} = 10kg. How long will it take the boxes to move 3m if they are released from rest? F{A}= Forces acting on hanging object...
  22. T

    Solve Pulley Problem: Speed of Blocks After Moving Distance d

    Homework Statement Sorry guys but uploading the image didnt work so i post it on imageshack. Here is the link: http://imageshack.us/f/208/apib.jpg/ So the quastion is: In the image the pulley is a uniform cylindrical disk of mass m and radius r. The strings are massless and there...
  23. E

    Motor in a pulley system with weight help (Sort of a dynamics problem)

    Homework Statement At the instant shown, point P on the cable has a velocity 12 m/s, which is increasing at the rate of 6m/s^2. Determine the power input of motor M at this instant if it operates with an efficiency of 0.8. The mass of the block A is 50kg. I've attached a picture of the...
  24. E

    Engineering Motor and Pulley System with weight help (Kind of a Dynamics Problem)

    Homework Statement At the instant shown, point P on the cable has a velocity 12 m/s, which is increasing at the rate of 6m/s^2. Determine the power input of motor M at this instant if it operates with an efficiency of 0.8. The mass of the block A is 50kg. I've attached a picture of the...
  25. D

    Translational/Rotation Question (Pulley)

    Homework Statement Compound pulley with a mass (10kg) attached to outer drum R = Outer Radius (250 mm) r = Inner Radius (150 mm) Horizontal force of 250 N being applied at edge of inner drum Friction torque of 7 N m present Mass of pulley = 20 kg and it has radius of gyration of 160 mm...
  26. F

    Acceleration and tension of pulley system

    Honestly I'm not sure if I've made any mistakes here, but I've been having considerable difficulty with tension problems. This is also the first pulley problem I've attempted, so I'm sure I've made a blunder or two somewhere. If someone could review what I've done so far that would be very...
  27. E

    Finding Tension T1 in a Pulley System

    A pulley is massless and frictionless. The masses 2 kg, 3 kg, and 6 kg are suspended as in the figure. (Figure Attached) What is the tension T1 in the string be- tween the two blocks on the left-hand side of the pulley? The acceleration of gravity is 9.8 m/s2 . Answer in units of N...
  28. M

    Pulley Free Body Diagram Problem

    In the figure below, m1 = 10.5 kg and m2 = 3.5 kg. The coefficient of static friction between m1 and the horizontal surface is 0.50, and the coefficient of kinetic friction is 0.30. I've drawn the free body diagram myself and labeled it but don't know how to structure the equations and stuff...
  29. D

    Cord tension & how to calculate force magnitude of a cord & pulley

    Homework Statement A man sitting in a bosun's chair that dangles from a massless rope, which runs over a massless, frictionless pulley and back down to the man's hand. the combined mass of the man and chair is 103.0 kg. With what force magnitude must the man pull on the rope if he is to rise...
  30. A

    I have a question about pulley

    Hi I have a question about pulley. There is fixed pulley: http://en.wikipedia.org/wiki/File:Polea-simple-fija.jpg http://en.wikipedia.org/wiki/File:Polea-simple-fija.jpg where you need to use e.g. 100N to lift 100N. There is moveable pulley: http://en.wikipedia.org/wiki/File:Pulley1a.svg...
  31. J

    Solve 3 Mass, 3 Pulley Homework

    Homework Statement -------------- I I I = string O O O = massless frictionless pulley I II I ' O " . = mass 1 : : = mass 2 " = mass 3 Find acceleration of each mass. Homework Equations F=ma conservation of...
  32. H

    Mechanical advantage and force analysis of complex pulley systems

    Homework Statement These are two of the excercises where I'm supposed to calculate the mechanical advantage of the pulley systems. Excuse the crude MS paint drawings, I do not have access to a scanner or a proper camera. The red dots are where two cables connect. The Attempt at a...
  33. F

    Belt Drive Pulley: Mean Diameter 300mm, Angle 180°, 920 RPM

    Homework Statement A belt drive pulley has a mean diameter of 300mm, an angle of contact of 180° and rotates at 920 rpm. Smaller belt tension is 50 N and coefficient of friction is 0.3 Neglect centrifugal Homework Equations V=piND The Attempt at a Solution pi*(920/60)*0.3=14.45 ms...
  34. B

    Mechanics Pulley question

    Homework Statement A mass 4m lying on a rough horizontal table is connected by a string, passing over a pulley, to another mass 3 m hanging freely. The pulley (regarded as a disk) has mass 4 m and rotates freely about a polar axis parallel to the edge of the table. The coefficient of kinetic...
  35. T

    Pulley system (ideal pulley) Find the angle with vertical line

    Ideal pulley and strings, no friction.The pulley and the second string don't move. I need to find the numerical value of theta, the acceleration of the two blocks and the tensions.Accelerations and tension must be given in terms of m and g.I guess 2T1=T2 T1=m2*a m1*g-T1=m1*aTo find theta I need...
  36. K

    Two blocks of mass connect to a pulley

    Homework Statement Blocks of mass and are connected by a massless string that passes over the pulley in the figure . The pulley turns on frictionless bearings, and mass slides on a horizontal, frictionless surface. Mass is released while the blocks are at rest. Homework Equations...
  37. K

    [Math Verification] Massless Pulley - Acceleration of Block A & B?

    Homework Statement http://img152.imageshack.us/img152/8286/imag0103l.jpg *I'm aware my free body diagram is off and that normal force should be in the left quadrant. Homework Equations F=m*aThe Attempt at a Solution Would I be correct in saying.. Fg of A = mg * sin (20) = 2kg * 9.8 * sin...
  38. I

    Work to be performed by a pulley

    Hello, I have a doubt in this exercise because it does not relate the forces work to be done. "The system shown is at rest. Determine the amount of work must be developed to apply a downward vertical force on the sphere, so that the block come off the floor."...
  39. A

    Atwood machine with two holes in pulley.

    Homework Statement A system consists of a pulley and two masses m1, m2 haning from it as shown in the figure. The pulley is a disk of radius R with constant mass density that has two circular hole with radius R/2. Find the angular acceleration of the pulley. Figure attached. Homework...
  40. H

    Find the angula aceleration of the pulley

    Homework Statement The pulley consists of two disks which are both attached to each other. The total moment of inertia is: \displaystyle I=23\times {{10}^{-4}}Kg\cdot {{m}^{2}} You also know that: \displaystyle \begin{align} & {{m}_{1}}=0.8 \\ & {{m}_{2}}=0.5Kg \\ &...
  41. T

    Find velocity of hanging block in a pulley system

    A pulley is set up on the edge of a desk. A light string connects a 10 kg block laying on the desk to a 4 kg block hanging off the pulley. The only significant friction is with the desk, and the coefficient of kinetic friction is 0.20. Use the law of conservation of energy to find the speed of...
  42. S

    Pulley dynmamics involving acceleration and time-varying tension.

    I came up with this question while thinking about pulleys. Most textbook pulley problems involve the force on the load being equal to the load's weight so that there's no acceleration. But what if we had the following setup. There's an anchor on the ceiling and there's a heavy crate on the...
  43. W

    Simple Pulley System with Two Masses

    Homework Statement http://imgur.com/Y1Dua r = 0.2m I = 1.4kg m^2 m1 = 2kg m2 = 5kg h = 4m Homework Equations Δ(Gravitational potential energy) = m1*g*h - m2*g*h Δ(Kinetic energy) = (1/2)*m1*v^2 + (1/2)*m2*v^2 + (1/2)*I*(v^2/r^2) The Attempt at a Solution System is...
  44. R

    Mechanics - Pulley system finding coefficient of friction

    Homework Statement Homework Equations I believe: F = m . a Ffriction = μs . N Ffriction = μs . mg . cosθ The Attempt at a Solution I don't quite get how the equations above would give me an answer to the minimum friction required so that the farmer doesn't slip. I know Fl =...
  45. A

    Torque on a Non-Circular Pulley

    Homework Statement Homework Equations Shown BelowThe Attempt at a Solution I need to find the torque (or even better, velocity) as a function of position. Right now I have mass and centroid (to find the force of gravity on the pulley at any position). Not sure if the mass moment of inertia is...
  46. L

    Question from a non-engineer: Pulley Systems

    Hello from a non-engineer. This post has a very practical purpose: I'm about to move into a small loft apartment with high ceilings but limited living and closet space. I'd like to find some way to mount a pipe to the ceiling via pulleys and rope or cable that can be lowered and raised with a...
  47. L

    Kinetic Energy including a pulley

    Homework Statement Two blocks, of masses M = 2.0 kg and 2M are connected to a spring of spring constant k = 200 N/m that has one end fixed, as shown in the figure below. The horizontal surface and the pulley are frictionless, and the pulley has a moment of inertia I=0.005 kg.m^2 with radius...
  48. M

    How Do You Calculate Forces and Accelerations in a Two Block and Pulley System?

    1. A block with mass m1 is placed on an inclined plane with slope angle α and is connected to a second hinging block with mass m2> m1 by a massless cord passing over a small frictionless pulley. The coefficient of kinectic freiction between mass ma and the incline is negligible. Find: (a) the...
  49. S

    Two Masses in Pulley System (Rotational Dynamics)

    So I've been prepping for my Engineering Physics 1 final, and I've been having trouble with rotational motion problems, but this problem has been driving me crazy for the past two days: Homework Statement (I wanted to include a normal link to an image, but I'm a new member, so here's...
  50. P

    Why are the accelerations of blocks A and B different in this pulley problem?

    It is not actually homework, but a physics problem I have encountered. For ease of discussion, I am attaching the question [University Physics, Young and Freedman, 12th edition] and it's solution as appeared in the solutions manual. What I don't understand is: In section (c), how can the...
Back
Top