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. G

    Solving Mass-Acceleration Relationships for Objects Connected with Pulleys

    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 below. (a) If a1 and a2 are the accelerations of m1 and m2, respectively, what is the relation between these...
  2. J

    Gears & Pulleys for Compressor Pump Project

    hiya, i need some help for a project I am working on, basicly i have a compressor pump that runs at 500rpm and @ 12 hp. now the problem is (this is a theoretical problem) i have to power it using a 3480rpm ac motor which has to be less than 10 hp (cost reasons). rough calculations show...
  3. H

    Newton's laws / pulleys question?

    I have uploaded the problem here: http://i36.tinypic.com/mps9i.jpg These are the answers I have gotten so far: a) L1 = 2*P1 - P2 - x1 + (pi*R) L2 = 2*P2 + (pi*R) - x2 b) Forces on M1 --> M1*g downward, and T1 upward, which I think is equal to M2*g. Therefore a1 = [(M2 - M1)*g] / M1...
  4. D

    Kinetic Friction and Ropes and Pulleys

    1. Homework Statement Block A, on a horizontal table, has a weight of 4.91N is attached to a rope, that goes over a pulley, attached to Block B, that has a weight of 2.94N. Once block B is set into downward motion, it descends at a constant speed. Assume that the mass and friction of the...
  5. F

    Two pulleys system (please check my work)

    Homework Statement Find the acceleration of the system http://img266.imageshack.us/img266/4904/2pulleyszw9.jpg The rope is massless The mobile pulley is not massless, it weighs 20 grams. Find the accelereation of the system Homework Equations F=mg F=ma g = 9.8 The Attempt at a...
  6. T

    Acceleration of M1 in System of Pulleys

    Homework Statement Mass M1 and M2 are connected to a system of strings and pulleys as shown. The strings are massless and inextensible and the pulleys are massless and frictionless. Find the acceleration of M1. (image attached. just to clarify the image, the upper left pulley is fixed...
  7. A

    How Do You Solve Tension and Acceleration in a Two-Pulley System?

    Homework Statement Two blocks are connected by a rope that passes around two pulleys as indicated in the figure. (Attached) a. Determine the tension in the rope. b. Determine the acceleration of each block (Hint: The two blocks do not have the same acceleration). The Attempt at a Solution I...
  8. H

    Force problem involving two pulleys and three masses

    Homework Statement A block with a mass of 8.00 kg rests on a frictionless table. On both sides of the table are frictionless pulleys. Two hanging blocks are attached to the block on the table though these pulleys with two cords (one block on each side). On the left side of the table the...
  9. K

    Pulley Mechanics: Equal Forces on Spring Scale?

    Homework Statement A 100 gram mass is hanging vertically from a spring scale and exerts a certain force. Another 100 gram mass is set up in the following situation (there is a pulley, spring scale, mass, and ring stand holding up the spring scale): Do the weights on each setup exert equal...
  10. C

    How Do Newton's Laws Apply to a Pulley System with Unequal Masses?

    Homework Statement http://img213.imageshack.us/img213/6969/physicsproblemhq3.png A rope of negligible mass passes over a pulley of negligible mass attached to the ceiling as shown above. One end of the rope is held by Student A of mass 70 kg, who is at rest on the floor. The opposite end...
  11. S

    Pulleys, Force, and Acceleration

    Homework Statement Set up a pulley system and place two masses at rest. Give a quick tug on one mass, setting the system in motion. After release, does the system accelerate of move at a (relatively) constant velocity? Does it make sense? Question #2 Now substitute a heaver mass for one of...
  12. P

    Pulleys - find force to accelerate a block

    Homework Statement A force F acts to the right on a 5.65 kg block. a 2.29 kg block is stacked on top of the 5.65kg block and can slide on it with a coefficient of friction of .15 between the blocks. The table has a coefficient of friction of .18. G= 9.8 m/s^2 system is in equilibrium Find...
  13. dontdisturbmycircles

    Kinetics Question (Dependant motion, gravity, pulleys)

    I am in second year engineering and am trying very hard in this course. I just started doing problems regarding simple kinetics this morning and I am getting a lot of wrong answers. Originally I just claimed to myself that I had made simple math errors but understood the concepts. The math in...
  14. C

    Solving Pulleys and Forces Homework Problem

    Homework Statement An object of mass 12.5 kg hangs from very light pulleys as shown here: http://i26.tinypic.com/24lq5b4.jpg What force must be applied to the rope so that the mass stays at rest? Homework Equations Fnet = ma... The Attempt at a Solution I am really clueless when it...
  15. T

    Motion in 2 Dimensions - Inclined Plane Pulleys

    Homework Statement a Mess of 5kg is being hauled up a smooth invlined place at 30 degree to the horizontal with an acceleration of 1.5ms^-2 by mean of a string parallel to the incline: a) What is tension in the string Homework Equations Fnet= ma Rules of right angled triangles (SOC CAH...
  16. T

    Motion in 2 Dimensions - Pulleys

    Homework Statement Two masses A and B and of mass 1.6kg and 2.4kg respectively are connected be a light string which passes over a a frictionless trolley. Calculate: a) The accelaration of the 1.6kg mass. b) The tension in the string c) The net force on the 2.4kg mass d) The Kinetic Energy of...
  17. J

    Finding moments of pulleys with mass and tensions.

    A uniform Disk of radius 0.18 m is mounted on a frictionless, horizontal axis. A light cord wrapped around the disk supports a 0.57 kg object. When released from rest, the object falls with a downward acceleration of 2.6 m/s^2 What is the Moment of Inertia of the disk...
  18. M

    How Do You Calculate Tension and Acceleration in a Pulley System?

    Homework Statement Determine the tension developed in the cords attached to each block and the accelerations of the blocks. Neglect the mass of the pulleys and cords. I have attached the picture below. Homework Equations Fnet=ma The Attempt at a Solution W=mg=(6*9.8) I have no...
  19. W

    Newtons Law Problem: objects and pulleys

    Homework Statement three blocks attatched by cords that loop over frictionless pulleys. Block B lies on frictionless table, block a hangs off the left side of the table, while block c hangs off the right side. mass a= 6kg mass b= 8kg and mass c= 10kg. When the blocks are released, what is the...
  20. J

    Does Using a Pulley Affect Acceleration in a Frictionless System?

    With a mass on a frictionless surface connected to a string that is sent over and down to a mass. Would that increase or decrease the acceleration compared to the equation, a=g(m). I'm just stumped on how to think of this. The pulley is not included in the equation but how would I figure out...
  21. S

    Calculating Tension and Acceleration in a Two-Pulley System

    Hope someone can help me with this one. I have two blocks with m1 and m2 connected to two pulleys. I need to figure out T1, T2, a1, and a2 using only the values of g, m1, and m2. But I've been unable to come up with an equation that will work with it. I have a picture attached. I tried using...
  22. W

    Pulleys and blocks - find acceleration

    1. A pulley A on the end of a spring balance. On 1 end is a 16kg mass. On the other is pulley B. On one end of pulley B is a mass of 4kg. On the other end is pulley C. On one end of pulley C is a 1kg mass. On the other end is a 7/3kg mass. All pulleys are massless and frictionless. Find accn. of...
  23. N

    Hooks and pulleys (torque and force)

    [SOLVED] Hooks and pulleys (torque and force) Homework Statement Two weights are connected by a very light flexible cord that passes over a 50.0N frictionless pulley of radius .300m. The pulley is a solid uniform disk and is supported by a hook connected to the ceiling. What force does the...
  24. K

    What kinds of local stores sell pulleys?

    What kinds of local stores sell pulleys? I can't buy online because of time limit. Are the like physics stores around cities? Or do like Arts & Crafts stores sell them? 91739
  25. S

    How Do Tensions on Either Side of a Rotating Pulley Compare?

    Homework Statement A rope passes over a 10-cm-diameter, 2.0 kg pulley that rotates on frictionless bearings. A graph shows the pulley's angular velocity as a function of time. The graph increases from (0,0) up to (3,120) linearly. Basically, there is a pulley with a rope thrown over it such...
  26. C

    Solving Homework Problem: Masses, Pulleys, and Forces

    Homework Statement The problem seems like this: on the left, closer to the floor, is block3 with mass 1.0kg, there is a string above it which connects it to block2 with mass 3.0kg which has a string above it that circles around a pulley and comes back down connecting it to block1 with mass...
  27. C

    Kiteboarding problem using weights and pulleys

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  28. D

    How do you calculate acceleration and angular acceleration with pulleys?

    Homework Statement A block has a mass of 500 g, another block has a mass of 460 g. Both are attached to a pulley with a frictionless wire that does not slip. The pulley, which is mounted in horizontal frictionless bearings, has a radius of 5.00 cm. When released from rest, the heavier block...
  29. G

    Calculate Acceleration of 2.0kg Block w/ Pulleys & Blocks

    Homework Statement What is the acceleration of the 2.0 kg block across the frictionless table http://s167.photobucket.com/albums/u143/grapz720/?action=view&current=phy.jpg Homework Equations I know the acceleration is positive for one block and negative for the other. F= ma , also...
  30. Q

    How Do You Calculate the Acceleration of a Mass in a Pulley System?

    Homework Statement A 1.0 kg mass (mA) and a 4.0 kg mass (mB) are attached to a lightweight cord that passes over a frictionless pulley. The hanging masses are free to move. Find the acceleration of the larger mass. Homework Equations Fnet = ma = FB-FA Fhanging object=m x acceleration...
  31. M

    Interacting Systems - Acceleration and Pulleys

    Homework Statement In the figure (attached), find an expression for the acceleration of m_1 (assume that the table is frictionless). Homework Equations Fnet = (m)(a) The Attempt at a Solution So I am assuming that the Fnet for the box m1 is T, which would be related to the...
  32. E

    Calculating Acceleration and Tension in a Pulley System with Inclined Planes

    Please help me because my teacher has not explained how to do questions involving angles. Blocks X and Y of masses mx=5.12kg and my=3.22kg are connected by a fishing line passing over a frictionless pulley. Show that block X slides up the incline (35.7 degrees above the horizontal) with...
  33. N

    Solving Physics Problem: Find a_2 of 2 Blocks, 2 Pulleys

    A block of mass m_1 is attached to a massless, ideal string. This string wraps around a massless pulley and then wraps around a second pulley that is attached to a block of mass m_2 that is free to slide on a frictionless table. The string is firmly anchored to a wall and the whole system is...
  34. D

    Rotational Motion- Pulleys with Friction

    Homework Statement Two Masses are suspended from a pulley. The pulley itself has a mas of .20kg a radius of .15m a constant torque of .35 MN due to the friction between the rotating pulley and its axle. What is the magnitude of the acceleration of the suspended masses if m1= .4kg and m2= .8...
  35. A

    Pulleys and Gravity: Solving Acceleration for m1 & m2

    In Figure P4.30, m1 = 9.5 kg and m2 = 3.5 kg. The coefficient of static friction between m1 and the horizontal surface is 0.60 while the coefficient of kinetic friction is 0.30. (Why can't I post this image in the message?) In case you don't feel like looking at the picture, there are two...
  36. G

    Newton's Laws; ramps and pulleys

    Homework Statement http://img201.imageshack.us/img201/6315/diagramyk1.gif -Assuming the system is frictionless, find m2 when it is accelerating down the ramp at 3.4 m/s2. Homework Equations -... F = ma? The Attempt at a Solution -In this problem, I tried tilting the axis so the...
  37. M

    Calculating the Speed of a Mass Rising on Two Connected Pulleys

    Homework Statement In my book, this question is accompanied with a diagram. But I will try to explain the diagram as best as I can. There are two pulleys A and B connected with a single thread. One end of thread, P, is along the pulley A, and the other end, Q, along B. Now let us take a...
  38. P

    Physics help on pulleys and tension

    2000M3. A pulley of radius R1 and rotational inertia I1 is mounted on an axle with negligible friction. A light cord passing over the pulley has two blocks of mass m attached to either end, as shown above. Assume that the cord does not slip on the pulley. Determine the answers to parts (a)...
  39. D

    Pulleys: How do they exactly work?

    Having multiple pulleys reduce the amount of force you have to exert to pull up an object? why is that exactly? I mean, I use this principle whenever I encounter a pulley Q...w/o really understanding why that's the case... Can someone expain in terms of Newtoniam mechanics and/or Free...
  40. A

    Mechanics question involving pulleys: where is the problem?

    Question A string is hung over a fixed pulley, and a 4kg mass is suspended from one end of the string. The other end of the string supports a massless pulley, over which a second string is hung. This string has a 2kg mass attached to one end, and a 1kg mass attached to the other end. See the...
  41. S

    Rotational motion of pulleys influenced by gravity. Not sure how to set up.

    I've attached the problem as a .jpg file. The mass obviously has potential energy. Is this simply converted to the kinetic energy of the mass plus the two kinetic energies of the pulleys? I also don't see how I would find the angular speed (probably don't even need to) of the pulleys. Cant...
  42. S

    Tractor and pulleys - expression of speed

    Homework Statement A tractor named A is used to lift a bale B with a system of pulleys. The tractor has an unknown speed called VA : find the expression of the bale's vertical speed VB in function of x (distance from the tractor to the pulley). The diameter of both pulleys can be...
  43. J

    Can Gravity Be Used to Rotate Pulleys?

    Cross section of pulley1, pulley2 , pulley3 and pulley4 are as shown in figure. Centres of Pulley 1 and pulley 2 are placed on same horizontal line. Centres of pulley 1 and pulley 2 are fixed. Pulley 1 and pulley 2 can rotate about their centre. Centres of pulley3 and pulley4 are also placed on...
  44. V

    Another problem with pulleys

    Two masses are connected as shown at http://viewmorepics.myspace.com/index.cfm?fuseaction=viewImage&friendID=128765607&imageID=1423595691 It is problem 15 I drew my free body diagrams, but I can't figure out the relationship to write for the pulley since the incline is frictionless. I know...
  45. mbrmbrg

    Work with Pulleys: Questions & Answers

    In Figure 7-48 (see attatched), a cord runs around two massless, frictionless pulleys. A canister with mass m = 11 kg hangs from one pulley, and you exert a force F on the free end of the cord: (a) What must be the magnitude of F if you are to lift the canister at a constant speed? (b) To...
  46. M

    Torque with pulleys and bucket of water

    Imagine a frictionless pulley (a solid cylinder) of unknown mass M and radius r = 0.41 m is used to draw water from a well. A bucket of mass m = 1.53 kg is attached to a cord wrapped around the cylinder. A bucket starts from rest at the top of the well and falls for t = 2.04 s before hitting the...
  47. P

    Strings and Pulleys - Find the energy

    Three objects with masses m1 = 7.0 kg, m2 = 10.0 kg, and m3 = 14.0 kg, respectively, are attached by strings over frictionless pulleys, as indicated in Figure P5.32. The horizontal surface is frictionless and the system is released from rest. Using energy concepts, find the speed of m3 after it...
  48. Z

    Help: Apply tension into equation for multiple pulleys

    I have this problem for homework. Find the magnitude of the minimum force F that allows the window washer to move upward. Express your answer in terms of the mass M and the magnitude of the acceleration due to gravity g. The professor didn't go over multiple pulleys though so I am...
  49. R

    Solving Forces with Pulleys: 420N & 190N Blocks

    so i have this problem with a block sitting on a horizontal surface and this block(m1) has the weight of 420 N. This block is connected by a string to a pulley and then connects to another block(m2) that is hanging from the pulley. The weight of the hanging block is 190 N. Ignore all...
  50. M

    Calculate Upper Scale Reading for Suspended 50kg Crate Using Spring Scales

    A 50-kg crate is suspended between the floor and the ceiling using two spring scales, one attached to the ceiling and one to the floor. If the lower scale reads 121 N, what is the reading of the upper scale? Ignore the weight of the scales. So, I convert 50kg to N and get 490 Then I subtract...
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