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. A

    Inextensible cords passing over frictionless pulleys

    Homework Statement the blocks shown in the figure are connected by flexible, inextensible cords passing over frictionless pulleys. at A, the coefficient fiction is 0.30 while at B, it is 0.40. compute the magnitude and direction of the friction forces and each block. am i right ? x( please...
  2. 1

    Blocks, pulleys, more friction woes

    Homework Statement Body A weighs 100 N, and body B weighs 35 N. The coefficients of friction between A and the incline are μs = 0.56 and μk = 0.25. Angle θ is 40°. Let the positive direction of an x-axis be up the incline. Find acceleration along x. Homework Equations The...
  3. D

    How Do You Calculate Tension in a Pulley System?

    I need some help with this problem. I can find the acceleration, just not the tension force. The mew kinetic is .6. The mass on the table is 10 kg and the mass hanging on the pulley is 20 kg. Thanks a ton.
  4. L

    Derive the displacements movable pulleys.

    Homework Statement Obtain the accelerations of mass a and mass b. Homework Equations Once i derive the displacement relation constraint, then i just have to diff twice w.r.t time. This part is ok. The Attempt at a Solution I am trying to reason this way: suppose 2M moves up by x...
  5. J

    Solving Tension in Massless, Frictionless Pulley System

    Homework Statement What is the tension T? The pulley is massless and frictionless. m1=661 g, w2=5 N, g=9.8 m/s2 Picture attached Homework Equations T=w1+w2 ?? The Attempt at a Solution First of all, I converted 661 g into kg. Next I multiplied that by g. I added that value to...
  6. M

    Overhead crane and pulleys problem

    The problem bellow is a real problem and I would like to get some ideas in order to overcome it. As you can see in the attached doc, we have two winches ( drum 1 and 2 ) on the same shaft of motor M1, two moving pulleys ( 3 and 4 ) and a fixed pulley (5). The load is 130 Tons, and we can...
  7. M

    Why Does the Load Measurement Vary with Crane Movement?

    The problem bellow is a real problem and I would like to get some ideas in order to overcome it. As you can see in the attached doc, we have two winches ( drum 1 and 2 ) on the same shaft of motor M1, two moving pulleys ( 3 and 4 ) and a fixed pulley (5). The load is 130 Tons, and we can...
  8. M

    Why Does a Crane's Load Cell Show Different Weights While Lifting and Lowering?

    As you can see in the attached doc, we have two winches on the same shaft of motor M1, two moving pulleys ( 3 and 4 ) and a fixed pulley (5). The load is 130 Tons, and we can measure that with a load cell at pulley 5 ( 32,5 Tons) when we stop the lifting of the load. But when the load is...
  9. B

    Find Acceleration of m_1 & m_2 in Frictionless Pulley System

    Homework Statement A pulley has a moment of inertia of 5.0 kg*m^2 and a radius of 0.5m. The cord supporting the masses m_1 and m_2 does not slip, and the axle is frictionless. Find the acceleration of each mass when m_1 = 2.0 kg and m_2 = 5.0 kg. Homework Equations F=ma, Fr=I(alpha)...
  10. O

    Belt friction between two pulleys.

    Homework Statement http://imageshack.us/m/135/2262/beltz.jpg I do no understand as shown in the above picture why T1 = 1 to make e^u0 = e^-u0, could anyone offer an explanation as to why this is the case? Thanks Homework Equations All above The Attempt at a Solution
  11. Y

    How Is Angular Velocity Affected by Torque in a Multi-Pulley System?

    Homework Statement Q2: IF mA=2kg, mB=7kg, and mC=5kg. Starting from rest, if a torque of 5Nm is given at t=0 to pulley A about point A for 3 seconds. Determine the angular velocity of the 3 pulleys at t=3s. [PLAIN]http://img98.imageshack.us/img98/8214/unled2tw.png Homework Equations...
  12. C

    Mechanics - Springs and pulleys

    Homework Statement The Attempt at a Solution I could say that (A)(B) are correct and (C) is wrong and i know 4kg block will have acceleration but i don't know how to find it.
  13. P

    What is the mass of the box held by Guy 3 in a three-pulley system?

    Homework Statement Three guys hold up three boxes motionless on the pulley apparatus shown below. Guy 1 has a box with a mass of 40 kg, Guy 2 has a box with a mass of 100 kg, and Guy 3 has a box with an unknown mass. The boxes are, again, motionless. At some point they let go of them, but Guy 2...
  14. G

    How Do I Calculate the Acceleration of a System with 3 Masses and 2 Pulleys?

    Homework Statement Homework Equations Fnet=ma Fres=uFn Fg=mg The Attempt at a Solution ive been stuck on this for 2 days.. i tried splitting the problem into 2 weights and then considering the last mass but NOTHING. i tried SO MANY attempts NOTHING WORKS and its starting to make me angry...
  15. C

    Momentum & Pulleys Homework: Solving for Velocity

    Homework Statement The Attempt at a Solution Taking the pulley and strings, pan, ball, block as system ... momentum is conserved therefore in Y direction(vertical) ... -mv = -2mV + mV -mv = -mV v = V which is incorrect (as i expected as there has to be some loss of velocity...
  16. D

    Moment of Inertia and Pulleys

    Homework Statement Two rocks, with masses m1 and m2, are attached to the opposite ends of a rope that runs around the inner radius r of a pulley with moment of inertia I m1 = 10 kg m2 = 50kg I = 60 kg*m^2 r = 1 m I have to determine Tension for both masses and the angular...
  17. P

    Tension & Pulleys: Force, Acceleration & Magnitude

    1) What force does a spring scale measure? (I measured several different masses in different ways using pulleys and the spring scale always came up with the same number of Newtons, is this tension or what?) 2) Why, even when two different sized masses are hanged upon a pulley, the spring...
  18. P

    Tension and pulleys (not calculative questions)

    Homework Statement 1) What force does a spring scale measure? (I measured several different masses in different ways using pulleys and the spring scale always came up with the same number of Newtons, is this tension or what?) 2) Why, even when two different sized masses are hanged upon a...
  19. P

    Solving Mechanics Problem with Pulleys: Acceleration of 2.0 kg Block

    b]1. Homework Statement [/b] There is a 1kg block on top of a 2 kg block. The 2 kg block A rope pulls on the lower block with a tension force of 20N. The coefficient of kinetic friction between the lower block and the surface is 0.16. The coefficient of kinetic friction between the lower...
  20. J

    Equilibrium of a Pulley System

    Homework Statement The picture is located in the attachmentHomework Equations \sum t = 0 \sum Fx = 0 Although there are no horiz. forces in this problem \sum Fy = 0 The Attempt at a Solution I'm not sure how to start. On the top most pulley, I believe that there is a Tension T and a...
  21. P

    Masses on inclined planes and pulleys

    1. Two objects are connected via a pulley and some string. The 12 kg cart is on a frictionless 42 deg. incline while the 15kg block is on a horizontal surface having a coefficient of friction equal to 0.23. Determine the acceleration of the system of masses. 2. Fnet=ma 3. I first...
  22. Femme_physics

    Questions about statics, mechanics, pulleys

    Questions about statics, mechanics, pulleys... 1) Does the radius of a single, fixated frictionless pulley affect the force I have to apply on one side in order to reach equilibrium with a constant load on the other? Or, will I always have to apply the same amount of force on the other side in...
  23. Z

    Pulleys + Convex Mirror Reflection

    Homework Statement In the given arrangement pulley P1 and P2 are moving with constant speed vo downward and the centre of the pulley P lies on the principal axis of a convex mirror having radius of curvature R. Find the speed of image of pulley P when it is at a distance x from the surface...
  24. T

    Pulleys Dynamics: Solving a Homework Statement

    Homework Statement Not sure why, but I opened an old textbook (Dynamics - Engineering Mechanics, Meriam, 1980) and started paging through. I decided to try this problem (attached jpg) and got stuck. The problem asks for the acceleration of the center of mass of the system of 4 weights...
  25. C

    Conceptual torque problem with multiple sized pulleys

    Homework Statement This is a six part conceptual question that is not difficult. However, the last part I am struggling with. What is wrong with the following student's reasoning: "The clockwise torque is greater than the counterclockwise torque because the disk is accelerating clockwise. For...
  26. S

    Having trouble with Pulleys and FBD's(not homework)

    So up until now I have understood physics but we're on Pulleys now and the Free body diagrams are baffling me... My teacher just manages to pull formulae from his behinde and I can't seem to figure out how he derives them... like for acceleration of two objects suspended vertically from a pulley...
  27. E

    Creating Mechanical Disadvantage with Pulleys

    Hey guys, Is there a way to set up a pulley system that creates a mechanical disadvantage? My group and I are trying to produce a pulley system that, when a certain weight is attached, requires five times the amount of force to move the weight. I certainly know how to create a mechanical...
  28. D

    Atwood Machine, two masses + two pulleys (w/ mass)

    Homework Statement An Atwood machine is constructed using two wheels (with the masses concentrated at the rims). The left wheel (m1) has a mass of 2.1 kg and radius 21.44 cm. The right wheel (m2) has a mass of 2.8 kg and radius 33.94 cm. The hanging mass on the left (m3) is 1.53 kg and on...
  29. T

    HP or PWOER Loss between 2 different sized Pulleys?

    hello guys..! i have one pulley of 8" (Driver) and another one 10" (Driven) he driver pulley is driven by 2Hp motor, so is there any equation or formula to calculate the Hp loss or power loss from 2Hp?
  30. F

    How Do Pulley Motions Influence Particle Dynamics?

    I was helping my friend with some questions regarding motions of pulleys and i am came up with the following question which i couldn't think of an argument... please check Two particles A and B of masses M and m respectively are connected by an inelastic string which passes over a smooth...
  31. J

    How Do Pulley Systems Affect Block Acceleration?

    Homework Statement two blocks are arranged as shown in this diagram and held at rest -the table top is frictionless http://i55.tinypic.com/py894.jpg what would the accelerations be for each block when they are released?Homework Equations Fnet=maThe Attempt at a Solution edit: nvm, i solved...
  32. J

    Kleppner and Kolenkow - Pulleys

    Homework Statement Masses 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. http://img844.imageshack.us/img844/3758/cimg0572.jpg Homework Equations...
  33. T

    Three Blocks On Two Pulleys

    Homework Statement [PLAIN]https://wug-s.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?cc/DuPage/phys2111/fall/homework/Ch-05-Newtons-Laws/blocks_on_pulleys/12.gif In the above picture, the masses are M1 = 10 kg, M2 = 15 kg, and M3 = 25 kg. The pulleys and strings are massless, there is...
  34. G

    Three blocks, two pulleys, on a incline

    Homework Statement The suspended 2.29 kg mass on the right is moving up, the 1.3 kg mass slides down the ramp, and the suspended 7.7 kg mass on the left is moving down. There is friction between the block and the ramp. The acceleration of gravity is 9.8 m/s2 . The pulleys are massless...
  35. A

    Table and frictionless pulleys

    Figure 5-58 shows three blocks attached by cords that loop over frictionless pulleys. Block B lies on a frictionless table; the masses are mA = 4.40 kg, mB = 9.80 kg, and mC = 12.0 kg. When the blocks are released, what is the tension in the cord at the right? all i could do on this one is...
  36. A

    System of pulleys - General Understanding

    Homework Statement A person is pulling the cable with force T. Find T. http://img684.imageshack.us/img684/1959/drawing6pulleys.jpg Homework Equations Equilibrium Sum of forces y = 0 The Attempt at a Solution This is what I did...
  37. A

    Solving Pulley Problem: Find T1, T2, W1, W2, Alpha

    Homework Statement A patient's leg is held in position by 2 weights tht are connected through cables. The weight of the leg is W = 300N. L is the horizontal distance between the points where the cables connect with the leg (points A and B) and C is the center of gravity for the leg, located...
  38. T

    A problem of strings, pulleys and weights

    Homework Statement The fig has three masses m1 , m2 , m3 .. all of which are unequal. Find relation between masses so that m3 remains stationary. ( pulleys , strings are frictionless and massless) The Attempt at a Solution I thought if mass on both side are equal then the system...
  39. S

    Two objects attached by pulleys

    Homework Statement There are two objects attached by a pulled on a cline. please click the link to see the diagram. http://session.masteringphysics.com/problemAsset/1010976/24/MLD_2l_2_v2_2_a.jpg if m2 weighed 2 kg and m1 weight 6 kg, which direction does the static friction point for...
  40. T

    Solving Pulley Systems: Kinetic Energy and Lagrangian

    Hello guys! Another question appeared during the preparation for my exam . For some reason I don't feel 100% comfortable when dealing with systems including pulleys and masses. In the given exercise I'm supposed to calculate the kinetic energy T of the system (which ultimately leads to the...
  41. M

    Finding acceleration of two blocks with pulleys

    Homework Statement In terms of m_1, m_2, and g , find the acceleration of the first block in the figure . There is no friction anywhere in the system. http://session.masteringphysics.com/problemAsset/1038627/5/YF-05-71.jpg Homework Equations The Attempt at a Solution I know...
  42. M

    Engineering Pulleys connecting a motor and shaft - Determining loads in shafts

    Homework Statement A 5hp, 1755rpm, WEG Motor (part #00518OP3E184T) needs to turn another shaft that is 12" away at 1000rpm. Homework Equations Torque=HP*5252/RPM T=F*r -> F=T/r Drive Ratio = Driver Pitch Diameter/Driven Pitch Diameter Sum Forces Sum Moments The Attempt at a...
  43. P

    Energy and pulleys (Atwood's machine i think)

    Homework Statement The pulley in the diagram has a radius of 0.160 m and a moment of inertia 0.480 kg.m². The rope does not slip on the pulley rim. Use energy methods to calculate the speed of the 4.00 kg block just before it strikes the floor. Homework Equations The Attempt at a...
  44. S

    How to Solve Pulley and Normal Force Problems Using Newton's Laws

    Homework Statement An 80.0 kg student stands on a 20.0 kg platform and applies a steady downwards force of 300 N on a long rope; the rope extends up from the students hands passes over pulley#1 at the top and then under pulley #2; finally the rope is attached to the bottom of pulley #1, as...
  45. P

    Pulleys, torque and tension

    A 1.2 kg mass and a 7.1 kg mass are connected by a massless string over a pulley that is in the shape of a bicycle wheel (all mass is concentrated at the rim) having a radius 0.25 m and mass 4.6 kg. Determine the time for the masses to move 2.6 m starting from rest. A. 2.714 sec B. 0.223...
  46. M

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

    Diagram Homework Statement Consider the two body system above. There is a 0.25kg object accelerating across a rough surface. The sliding object is attached by a string to a 0.1kg object which is suspended over a pulley. the coefficient of kinetic friction is 0.183. Calculate the...
  47. M

    How Do You Calculate Tension in a Pulley System with Friction?

    Diagram Homework Statement Consider the two body system above. There is a 0.25kg object accelerating across a rough surface. The sliding object is attached by a string to a 0.1kg object which is suspended over a pulley. the coefficient of kinetic friction( arrow on diagram) is 0.183...
  48. R

    Help with 2 pulleys 2 objects.

    Homework Statement An object of mass 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. (a) If a1 and a2 are the accelerations of m1 and m2, respectively, what is the relation between these accelerations? Express...
  49. S

    What is the acceleration of a system of blocks and pulleys?

    Homework Statement Blocks with masses of m1= 1.0 kg and m2 = 2.0 kg are connected by a string, supported on a frictionless table, and connected by a string and pulley to a hanging block with a mass m3 = 3.0 kg, as shown (attached the doc), and released from rest. Homework...
  50. P

    Solving Pulleys with Masses: Find Force T in N

    Homework Statement The system is in equilibrium and the pulleys are frictionless and mass less. Find the force T. The acceleration of gravity is 9.8 m/s2 . Answer in units of N. Homework Equations F=ma The Attempt at a Solution Okay so I looked at this problem and I thought that...
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