What is Pulleys: Definition and 381 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.

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  1. D

    Dynamic motion involving pulleys and friction.

    Homework Statement http://img689.imageshack.us/img689/2315/dynamicsproblem.jpg" Homework Equations The Attempt at a Solution FC = FfB mC * 9.81 = (6.0)(9.81)(0.30) mC = 1.8 <---- :( Obviously that was wrong haha. I then tried to figure out how the pulley affects the...
  2. F

    Static Equilibrium components (pulleys, weights)

    Homework Statement Component diagram: include all forces, x & y, angles compare x components (are they equal?) do y-components equal 0? Homework Equations Fnet = ma = 0 = F + F + F... SOHCAHTOA The Attempt at a Solution Attached is my diagram with components drawn in. There...
  3. M

    System with two boxes and pulleys

    Homework Statement We have a system which look like this: http://img535.imageshack.us/img535/9153/16234612.jpg The two boxes is connected by a wire without mass. The big box on the left has the mass 2m, the small box on the right has mass m. The right pulley has radius r has mass m...
  4. Z

    Pulleys and Conservation of Energy

    1. In the system shown in the figure, the pulleys on the left and right are fixed, but the pulley in the center can move left or right. The two hanging masses are identical, and the pulleys and ropes are all massless. Find the upward acceleration of the mass on the left, in terms of g. 2. I have...
  5. T

    What is the Force Exerted by a Pebble on a Block in an Ideal Atwood's Machine?

    Homework Statement A pebble of mass m rests on the block of mass of m2 the ideal Atwood's machine in the figure below. Find the force exerted by the pebble on the block of mass m2. (Use the following variables as necessary: m for m, m_1 for m1, m_2 for m2, and g for gravity.) Homework...
  6. J

    Masses and Pulleys on a table

    1. Find the horizontal displacement of a 24kg mass on a tabletop as a 5.4kg mass drops 8.4cms. they are connected by a string, run through a pulley. The string and pulley are mass less and frictionless. Then find the acceleration of the 24kg mass. Then find the tension of the string between...
  7. S

    Equilibrium in a tractive apparatus - tension and pulleys

    Homework Statement Determine the magnitude and direction (theta) of F in the diagram of Homework Equations ΣFx = 0 ΣFy = 0 F = ma The Attempt at a Solution I tried using the sum of components but I end up with three variables and two equations. I've always had issues with...
  8. A

    Atwood's Machine with 3 pulleys

    Homework Statement There are three pulleys in this system. The leftmost pulley is attached to ceiling. It has a string running through it with a mass of m attached. The rightmost pulley is also attached to the ceiling. It has the same string running through it with a mass of 3m attached. In...
  9. Z

    Solve Two Pulleys Problem: Find Minimum Tension Needed

    Hi, i am preparing for the test and have a problem with the following question. a crate is pulled up using frictionless pulleys in the manner shown in the image attached. the angle is teta=37 deg. the small pulley mass is m1=3.1 kg for the traveling pulley m2=6.9 kg. the mass of the crate is...
  10. J

    How Do Pulley Velocities and Positions Relate in Dependent Motion?

    The slider block B moves to the right with a constant velocity of 20in/s. Determine (a) the velocity of block A, (b) the velocity of portion D of the cable, (c) the relative velocity of A with respect to B, (d) the relative velocity of portion C of the cable with respect to portion D. Two...
  11. B

    Solving Pulleys and Tension Problems

    This is incredibly simple, but i cannot remember the formula for tension, which is a show stopper. Homework Statement Simple pulley. Two masses attached with a string running over a frictionless wheel. m1 is 8kg and m2 is 12kg. I need to find acceleration and tension over the...
  12. J

    Velocity of a block on an inclined plane with pulleys

    Hey all. I'm new to this forum and by the looks of it, a lot of you really know your physics. I was hoping for some help on this problem I can't figure out. I think I haven't fully grasped all the concepts involved in this question. Homework Statement Determine the velocity of the 51-lb block...
  13. P

    Frictionless Pulleys With Three Objects - Am I Right?

    I just want to check whether my answer is right because this worksheet has no answers. Thanks. The following system of masses are connected by light inextensible strings as shown in the diagram. The string connecting the 5.0 kg mass to the 8.0kg mass passes over a frictionless pulley...
  14. G

    Pulleys question - Need a rig to lift with a MA=107?

    Hi I have an installation/art project that requires a rig designed to balance a weight of 3200lbs using a weight of 30lbs. I think that means a mechanical advantage of 107 if using pulleys? Both weights would be suspended in the air by the rig so that someone pulling on the small weight would...
  15. S

    Dynamics of Particles : Problems involving pulleys.

    Homework Statement Two particles P and Q of masses 1 kg and 2kg respectively are hanging vertically from the ends of a light inextensible string which passes over a smooth fixed pulley. The system is released from rest with both particles a distance of 1.5 m above a floor. When the masses...
  16. W

    How Do Mechanical Advantages Affect Accelerations in a Pulley System?

    Homework Statement The original question is: What are the accelerations of the two masses? Given: M=8kg m=3kg g=10m/s^2 Fapp=120N Assume all pulleys and strings are massless and frictionless My problem is whether there is a mechanical advantage in the question so I should...
  17. S

    Pulley System: 2 Masses & 4 Pulleys

    This isn't a homework question, I just thought of it but don't know how to model the situation Given a pulley system like this http://img101.imageshack.us/img101/2106/pulleys.png suppose the string is massless and the pulleys are massless and frictionless. say m2 is greater than m1, each...
  18. R

    Three Blocks Two Pulleys and a Table

    This was a problem on an exam I had the other day and I want to know if my attempt was correct. Homework Statement Please look at the attached image. You have a system of two ideal pulleys set up on a table. Block A is hanging from a string on the left side of the table which passes by a...
  19. M

    What is the speed of M2 at t=1.75 s in a system of three blocks and two pulleys?

    Homework Statement three blocks are relased at t=0 from the position shown in the figure. Assume that there is no friction between the table and M2, and that the two pulleys are massless and frictionless. The masses are: M1 = 3.0 kg, M2 = 9.0 kg, M3 = 5.0 kg. M2 is the middle block...
  20. F

    Blocks and Pulleys Problem,

    Three Blocks total, Two on sides hanging off the table, and one Block on table in the middle of the two outer blocks. . . symmetrical. block1 from left has a mass of M, hanging and connected to a pulley, which is the connected to Block 2(on a table) with Mass of 2M, Block three is also...
  21. L

    Newtons Laws applyied to pulleys

    Homework Statement There is a drawing with a block weight 416N on a table attached to a string that is running through a pulley at the end of the table. On the other end of the string a block that is hanging off the side of the table with a weight of 215N. Ignore all frictional effects and...
  22. S

    How Do Pulleys Affect Work and Energy in Lifting a Load?

    Homework Statement A box of mass m can be lifted using a rope and two pulleys, as shown. http://bcs.whfreeman.com/WebPub/Physics/tiplerphysics6e_bridge/question_bank_images/6-36.png?1341 You exert a force of magnitude F on the free end of the rope. Give your answers in terms of h and w.1...
  23. A

    What are the weights A and B in this system?

    Homework Statement For some reason, this question's really stumped me. The text reads: "The system shown is in static equilibrium. Use the principle of virtual work to find the weights A and B. Neglect the weight of the strings and the friction in the pulleys." And has the accompanying...
  24. H

    Help with a physics problem, pulleys and acceleration

    Homework Statement A window washer pulls herself upward using the bucket-pulley apparatus shown in Fig. 4-48. The mass of the person plus the bucket is 61 kg. (a) How hard must she pull downward to raise herself slowly at constant speed? 298.9 N (b) If she increases this force by 12%, what...
  25. C

    Solving Pulley & Block Problems: Acceleration of A

    Homework Statement Body A in Fig. 6-36 weighs 102 N, and body B weighs 32 N. The coefficients of friction between A and the incline are μs = .56 and μk = 0.25. Angle θ is 40°. Let the positive direction of an x-axis be down the slope. What is the acceleration of A if A is initially (a) at...
  26. M

    How Is Tension Calculated in an Atwood's Machine?

    Homework Statement The figure shows two blocks connected by a cord (of negligible mass) that passes over a frictionless pulley (also of negligible mass). The arrangement is known as Atwood's machine. Block 1 has mass m1 = 0.900 kg; block 2 has mass m2 = 2.70 kg. What is the tension in the...
  27. G

    Pulleys, tension, and blocks oh my

    Homework Statement In the figure, the pulleys and the cords are light, all surfaces are frictionless, and the cords do not stretch. (a) How does the acceleration of block 1 compare with the acceleration of block 2? (Use a_2 for a2.) (b) The mass of block 2 is 1.22 kg. Find its acceleration as...
  28. C

    Forces and Pulleys of two blocks

    Homework Statement Two blocks are connected by a rope that passes over a set of pulleys. One block has a weight of 412N and the other has a weight of 908N. The rope and the pulleys are massless and there is no friction. (a) What is the acceleration of the lighter block? (b) Suppose that the...
  29. H

    Two blocks on top of eachother with pulleys

    Homework Statement A 3.0-kg block sits on top of a 5.0-kg block which is on a horizontal surface. The 5.0-kg block is pulled to the right with a force F. The coefficient of static friction between all surfaces is 0.60 and the kinetic coefficient is 0.36. a)What is the minimum value of F...
  30. B

    System of pulleys - find acceleration

    Homework Statement An object of mass m1 on a frictionless horizontal table is connected to an object of mass m2 through a very light pulley P1 and a light fixed pulley P2 as shown in Figure P5.34. (a) If a1 and a2 are the accelerations of m1 and m2, respectively, what is the relation...
  31. T

    Classical Mechanics - Pulleys System

    Homework Statement Consider the pulleys system in the picture. Assume both pulleys are frictionless. Assume the rope is massless and inextensible. Find the acceleration of the mass m_2 Homework Equations The Attempt at a Solution I have solved the same problem with massless...
  32. P

    Solving Acceleration of M1: Blocks and Pulleys

    Homework Statement Blocks of mass M1 and m2 (as shown in attachment) are connected by a system of frictionless pulleys by massless strings. What is the acceleration of M1? Homework Equations The Attempt at a Solution Let T1 be the tension in the first (higher) string, and T2 be...
  33. X

    What is the required force to lift oneself using movable pulleys?

    1. Homework Statement In the figure below, the man and the platform together weigh 780 N. The pulley can be modeled as frictionless. Determine how hard the man has to pull on the rope to lift himself steadily upward above the ground. ____________N 2. Homework Equations...
  34. M

    Complex Pulley System (five different pulleys)

    Homework Statement We are asked to find the force (F) needed to maintain equilibrium. I've drawn a picture; the red, blue, and green ropes are three separate ropes. Block W has a weight of 500 lbs, pulley A has a weight of 10 lbs, and pulley B has a weight of 20 lbs. the picture...
  35. I

    What are the equations for tension and acceleration in a pulley system?

    Homework Statement A light cable passes over a frictionless pulley attached to the ceiling. A 10 kg block hangs at one end of the cable and an 8 kg block connected by a light cable to a 4 kg block hangs at the other end. a) Construct a force diagram for each block. b) Write Newton's...
  36. I

    Problem involving two pulleys

    Mass m1 on a frictionless horizontal table is connected to mass m2 by means of a very light pulley P1 and a light fixed pulley P2 as shown in Figure 1. (a) If a1 and a2 are the accelerations of m1 and m2 , respectively, what is the relationship between these accelerations? Express (b) the...
  37. T

    Newton's Third Law - Using pulleys and slopes

    Homework Statement A 5.9 kg box is on a frictionless 40 degree slope and is connected via a massless string over a massless, frictionless pulley to a hanging 2.1 kg weight. A. What is the tension in the string if the 5.9 kg box is held in place, so that it cannot move? B. If the box is...
  38. X

    Angular Acceleration, 2 Pulleys on common axle

    Note: This is similar to 2 previous questions I've seen here (https://www.physicsforums.com/showthread.php?t=261193"), and while this is my first post, I've lurked/found this site to really be helpful in getting me to be able to figure out how to solve problems I have with my physics homework...
  39. Saladsamurai

    Discovering the Keq of a System: Understanding Pulleys and Springs

    So I am trying to follow along this example in the text to find keq of the system. I can follow everything up until the point that they say: "It follows that x=2(x1+x2) where: x = displacement of mass x1 =displacement of Pulley1cm x2 =displacement of Pulley2cm I am not...
  40. E

    True-false questions about frictionaless, masslesss pulleys

    Homework Statement These are true/ false questions, equal to, >, or < A frictionless, massless pulley is attached to a ceiling, Mass m2 is greater than mass m1. A. The magnitude of the acceleration of m2 is ... the magnitude of the acceleration on m1. B. The center of mass accelerates...
  41. M

    Test Question - Pulleys and Rubberbands

    I missed this question on the test and I don't get it... I attached a scanned image of the question. If you can't make out the text it reads: Two identical rubber bands connect masses A and B to a string over a frictionless pulley of negligible mass. The amount of stretch is greater in the...
  42. Z

    How Is Velocity Calculated for a 5kg Block in a Pulley System with a Spring?

    1. A pulley has a massless in extensible thread whose one side has a 5 kg block along with a spring of k=40 with it and the other end has a 2kg block (which is on the ground ). Find velocity of the 5kg block when the 2 kg block moves up. The Equations part : taking Tension as T , and...
  43. M

    3 masses attached by rope on table with 2 pulleys.

    Homework Statement You have 3 masses. M1 = 4 kg. M2 = 1kg. M3 = 2kg, M1 is attached to M2 by a rope. M2 is attached to M3 by a rope. M1 is hanging from a pulley attached to the left end of a table, M2 is on the table, and M3 is hanging from a pulley attaced to the right end of the table. The...
  44. S

    Tension force with pulleys and weights

    Homework Statement An accident victim with a broken leg is being placed in traction. The patient wears a special boot with a pulley attached to the sole. The foot and boot together have a mass of m = 3.4 kg, and the doctor has decided to hang a 6.0 kg mass from the rope. The boot is held...
  45. G

    Understanding Mechanical Advantage in Pulley Systems

    Let's say I have a 2-pulley system, with the effort force F being pulled upwards. The load is attached to the lower movable pully P1 where the rope is fixed. The rope extends up to the fixed pulley on the ceiling P2, wraps around, then travels back down to the side of the lower pulley, wraps...
  46. X

    Why do rotating pulleys have different tensions on either side?

    Dear All, Suppose there is a a pulley with mass and a massless cord around it, if pulley is rotating then I have learned that there are different tensions on either side of the pulley. I am having some trouble visualizing it. Moreover, if there are two different tensions on the cords, where...
  47. B

    Friction in Pulley System: Calculations?

    If a string around a pulley is pulled without slipping, I am wondering if there is any frictional force acting on the string by the pulley. If there is, will it appear in calculations? Thanks in advance
  48. M

    Forces- two pulleys w. diff accelerations

    Homework Statement In the drawing the rope and the pulleys are massless and frictionless, and there is no friction between the table and the block. Find the tension in the rope and the acceleration of the 10kg block. Here is my drawing of the problem and my FBDs and equations. I...
  49. S

    Frictionless pulleys with unknown masses. ATTEMPTED SOLUTION INSIDE

    Homework Statement Two masses are connected by means of a string which passes over a light frictionless pulley. The coefficient of kinetic friction between the 9kg mass and the table is 0.25. The applied force on the 9kg mass is unknown and the acceleration of the unknown mass, m, is 1m.s^2...
  50. K

    Atwoods MAchine with two pulleys and three masses

    Homework Statement A system contains two pulleys, over the first pulley there is mass 3, m_3, on one end of the rope. the other end of that rope is connected to the second pully. Hung on the second pulley are mass 2, m_2, and mass 1, m_1. Find the acceleration constraint in terms of a_1 and...
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