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. C

    Pulley problem solving for mass

    Movers have to haul a piano up to a window that is 5 floors above the ground. They decide to use a pulley system with 6 strands of rope. if the movers can exert a total force of 1111 N, how heavy a piano can they hoist? It doesn't say where the movers are standing but I'm assuming on the...
  2. T

    What is the equation for torque in a system with two blocks and a pulley?

    Homework Statement http://imgur.com/MaT4N Homework Equations Torque = Fr The Attempt at a Solution 1) I tried m2 g r - m1 g r = 1/2 M r^2 * (acceleration / r) didn't work 2)I tried replace the moment of inertia equation to above equation,still didn't work
  3. J

    Physics C mech 2004 FR (2) - Pulley and Rotational Inertia

    Homework Statement http://apcentral.collegeboard.com/apc/public/repository/ap04_frq_physics_cm_36191.pdf The problem can be found here. I am stuck on problem 2 d. Homework Equations I = m(g-a)R2 / a //found in part c The Attempt at a Solution I don't understand why the...
  4. E

    Simple Pulley Problem: Energy Methods and Coefficient of Friction Explained

    Homework Statement In Fig. 9.2, two blocks, of masses 2 kg and 3 kg, are connected by a light string that passes over a pulley of moment of inertia 0.004 kgm^2 and radius 5 cm. The coefficient of friction for the table top is 0.30. The blocks are released from rest. Using energy methods, one...
  5. C

    Torque, Rotation, Pulley problem

    [b]1. A 2.5 kg block and a 1.5 kg block are attached to opposite ends of a light rope. The rope hangs over a solid frictionless pulley that is 30 cm in diameter and has a mass of .75 kg. When the blocks are released, what is the acceleration of the lighter block. Ok, the book says 2.2m/s^2...
  6. M

    Weight on a pulley, torque, mechanical energy

    Homework Statement A block of mass (m1) is attached by a massless string to a pulley of mass (m2) with radius R. Starting from rest, what is the block's speed after it has fallen height h? Homework Equations I'll call angular velocity w. I'm thinking conservation of mechanical energy, so...
  7. H

    Pulley forces on truss crane problem.

    Hi for my design project at uni I am to design a truss crane to a certain spec. I can easily calculate the forces in a truss without the pulley systems. However when I have the pulleys I'm not sure how this affects the forces in the truss. I have the load attached via a 4 cable pulley at the...
  8. J

    Pulley Cable System (Conceptual)

    Homework Statement A window washer of mass M is sitting on a platform suspended by a system of cables and pulleys as shown . He is pulling on the cable with a force of magnitude F. The cables and pulleys are ideal (massless and frictionless), and the platform has negligible mass...
  9. G

    Forces in the triangle and pulley system

    Two blocks are connected by a string-one on an incline, the rope draped over a pulley, and one hanging from the string. The smooth inclined surface makes an angle of 35 with the horizontal, and the block on the incline has a mass of 5.7 kg. The mass of the hanging block is 3.2kg. Find the...
  10. I

    Does Pulley Mass Affect Rope Tension Symmetry?

    Hi there, If a pulley system made of 2 same mass blocks (on a a table, one hanging), a disk pulley with mass but no friction on the string nor pulley axis, does it mean that the Tension on the rope is the same on either side of the rope? Everywhere I've read implies this, and it makes sense...
  11. P

    I'm wondering about the theory behind pulley systems

    I'm just wondering if the tension between the masses, that is the tension from the string, is different between each mass in the following situations. Like is the T between m1 and m2 different from the T between m2 and m3? Is it for both situations or is the T the same all around in one of the...
  12. ThomasMagnus

    How can the window washer move at constant velocity with unbalanced forces?

    A window washer pulls himself upward using the bucket pulley apparatus shown. How hard must he pull downward to raise himself at a constant speed? The mass of the person and the bucket is 65kg. My attempt: When doing pulley problems, I like to set 'moving to the right' as positive. In this...
  13. E

    Work in Pulley System: What is the Total Work Done on the 20.0-N Block?

    Homework Statement Two blocks are connected by a very light string passing over a massless and frictionless pulley (Figure ). The 20.0-N block moves 75.0cm to the right and the 12.0-N block moves 75.0cm downward. Find the total work done on 20.0-N block if there is no friction between the...
  14. N

    Calculating Acceleration and Tension in a Pulley System

    Please refer to problem VI here: http://www.physics.ohio-state.edu/~dongping/phys131_winter2011/phys131/final-exam-practice-2011.pdf Use 10 for gravity if needed. Homework Statement 1. When the system is released from rest, what is the magnitude of the blocks' acceleration? 2...
  15. M

    Calculating load rating of a pulley stand

    Hi Guys, I'm a mechanical engineer looking for help with a structural problem, I work on-site at an iron ore mine in Western Australia. Typically once we design stands we get them fabricated then sent for certification. Certification involves a company putting the load which we wish to get...
  16. D

    How Do Pulley Systems Affect Tension Between Different Masses?

    Homework Statement In the figure here three ballot boxes are connected by cords, one of which wraps over a pulley having negligible friction on its axle and negligible mass. The masses are m1 = 28 kg, m2 = 45 kg, and m3 = 12 kg. When the assembly is released from rest, (a) what is the...
  17. M

    What are the effects of the mass of the pulley and string in Fletcher's trolley

    Homework Statement Homework Equations What happens if you take into consideration the mass of the pulley, the mass of the string, and the force of friction between the string and the pulley when you are doing a Fletcher's trolley question? The Attempt at a Solution i know that by taking...
  18. U

    What is the tension on a string wrapped around a pulley?

    Homework Statement [PLAIN]http://nicholascrumrine.net/otherpics/physics/HW4_6.jpg Homework Equations Sum(F)=MA w=v/r The Attempt at a Solution My assumptions are as follows: The sum of the tensions on the left side of the pulley is equal to the tension in right side of the...
  19. X

    Pulley on an inclined plane

    Homework Statement A frictionless pulley connects 2 masses, one of which is on a frictionless inclined plane at angle θ, as shown in the diagram. The pulley system is set up so it has a mechanical advantage of 2 (so that if m1 moves 1 meter, m2 will move only 0.5 meters). Find equations...
  20. J

    Angular Velocity On Pulley After Variable Force

    Homework Statement A pulley having a rotational inertia of 1.1 10-3 kg·m2 about its axle and a radius of 23 cm is acted on by a force, applied tangentially at its rim, that varies in time as F = 0.50t + 0.30t2, where F is in Newtons and t in seconds. If the pulley was initially at rest, find...
  21. M

    Solve Friction & Pulley Problem: Acceleration of Blocks

    Hello everyone... I need ur help in the following problem Homework Statement A perfect rope connects a 20 kg block to a 30 kg block. The rope passes over a perfect pulley at the top of a 53 ° incline. The 30 kg block rests on the incline and the 20 kg block hangs from the pulley. The blocks...
  22. M

    How Does Pulley Torque Affect Wire Tension in a Frictionless System?

    Homework Statement A 12.0kg box resting on a horizontal, frictionless surface is attached to a 5.00kgweight by a thin, light wire that passes without slippage over a frictionless pulley (the figure ). The pulley has the shape of a uniform solid disk of mass 1.70kg and diameter 0.600 m...
  23. D

    What Is the Speed of the Blocks When They Are at the Same Height?

    Homework Statement A system has two blocks connected by frictionless pulleys. One block (m = 3kg) is above the other (m = 2kg) vertically, as the other is lowered by a weight. Initially, they are 5m apart, vertically. When the weight is removed, what is the speed of the blocks when they are at...
  24. G

    Inclined Plane, 2 masses, 1 pulley - Friction

    Homework Statement A block with mass 10.7 kg is placed on an inclined plane with slope angle 24^\circ and is connected to a second hanging block that has mass 15 kg by a cord passing over a small, frictionless pulley. The coefficient of static friction is 0.47 and the coefficient of kinetic...
  25. D

    Help Tension and Acceleration of 2 masses with a pulley

    Here is the Please teach me how to solve this thanks!
  26. A

    Acceleration of a mass hanging from a pulley problem

    EDIT: I just realized I have to use the tension as the force and not simply mg. It's been a while since I dealt with these problems and that slipped my mind. I think I get it now, sorry. I can't figure out where I'm messing up on this. This is not a homework problem, bear with me as I try...
  27. S

    Blocks on pulley on incline plane

    Homework Statement M1 and M2 are two masses connected as shown. The pulley is light (massless) and frictionless. Find the mass M1, given that M2 (3.5 kg) accelerates downwards at 2.77 m/s2, θ is 25o, and μk is 0.37. Homework Equations F = ma F = mg Ff = μkNThe Attempt at a Solution...
  28. M

    Finding W1 & W2 Given Frictionless Pulley System

    In the figure shown the pulley are frictionless and the system hangs at equilibrium. If w3, the weight of the object on the right is 200N, what are the values of w1 and w2? http://img228.imageshack.us/i/74717268.png/ http://img228.imageshack.us/img228/2605/74717268.th.png Uploaded with...
  29. M

    What is the Tension in a Pulley System with Two Connected Masses?

    Homework Statement [PLAIN]http://img703.imageshack.us/img703/3580/12p71.jpg m1 = 1,378 g. It is free to move along a horizontal, frictionless surface. This block is connected to a second block with mass of m2 = 872 g by a massless string that extends around a massless, frictionless pulley...
  30. M

    What is the magnitude of acceleration in a system with two boxes and a pulley?

    Homework Statement http://img148.imageshack.us/img148/8686/ssslk.png the two boxes and the pulley have the same mass I=.5mr^2 the system is accelerating downwards calculate the magnitude of the accelerationHomework Equations The Attempt at a Solution I will call the falling one D and the...
  31. D

    Mass acceleration - pulley system - friction

    Homework Statement In Figure P4.25, m1 = 10.5 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. If the system is set in motion with m2 moving downward, what will be the acceleration of the...
  32. Z

    Pulley attached to two objects with a rope

    Homework Statement In the system shown in the figure , block A has mass = 2.00 , block B has mass = 0.360 , and the rope connecting them has a nonzero mass 0.240 . The rope has a total length 1.10 and the pulley has a very small radius. Let be the length of rope that hangs vertically...
  33. M

    Acceleration of pulley system physics problem

    Homework Statement In the figure, find an expression for the acceleration of m1 (assume that the table is frictionless).Homework Equations The Attempt at a Solution That picture of the second mass is stumping me because I have no idea what the heck is going on. It seems as if the second mass...
  34. J

    Simple concept help: Pulley and Net Torque

    Homework Statement A ball (hollow sphere) of radius .11m and mass .444kg is mounted on a frictionless axle. A massless cord is wrapped around the ball supporting an object of mass .02kg. Find the angular acceleration of the wheel, linear acceleration of the object and tension in the cord...
  35. H

    Calculating Time for a Mass to Hit the Floor on a Pulley System

    Homework Statement A 10.0 g mass is tied to a string. The string is attached to a 500.0 g mass and stretched over a pulley , leaving the 10.0 g mass suspended above the floor. Determine the time it will take the 10.0 g mass to hit the floor if it starts out 1.50m above the floor. Homework...
  36. K

    Acceleration of Two Masses on a Pulley with Moment of Inertia

    Homework Statement The pulley on the drawing has moment of inertia of I=kMR2. What's the acceleration. Homework Equations M=I\alpha F=ma The Attempt at a Solution m_1g-T_1=m_1a T_2-m_2=m_2a \mbox{ }R\alpha=a (T_1-T_2)R=kMR^2\cdot\alpha all these yield: a=\frac{g(m_1+m_2)}{kM+m_1+m_2}...
  37. A

    How Do Accelerations and Tensions Relate in a Dual Pulley System?

    Homework Statement An object of mass m_1 hangs from a string that passes over a very light fixed pulley P_1. the string connects to a second very light pulley P_2. A second string pases around this pulley with one end attached to a wall and the other to an object of mass m_2 on a...
  38. A

    Pulley Free Body Diagram and rope tension

    Homework Statement The figure above shows an 80 kilogram person standing on a 20 kilogram 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 person. The masses of the rope and pulley are negligible. You may use g...
  39. 1

    Exploring the Impact of a Frictionless Pulley on Acceleration

    Pretend there are two accelerating masses connected to a massless string with a frictionless pulley between them. How can the frictionless pulley (Rotational inertia and radius given) affect acceleration in any sort of way? Also, why is the net force equal to Acceleration * (Mass of two...
  40. A

    Tension in a string (inclined plane, pulley, friction)

    Homework Statement two blocks of mass m1 50kg and m2 100kg are connected by a string of negligible mass. The pulley is massless and frictionless. The coefficient of kinetic friction between the 50kg block and the incline is 0.250 the 100kg mass is the hanging mass. theta is 37.0 deg...
  41. V

    Non ideal pulley with two masses

    Hi, So I have a problem with a question upon reviewing a past physics final. Two boxes are connected by a massless, unstretchable rope that passes over a non-ideal pulley. The radius and mass of the pulley are R = 0.100m and M = 1.75 kg. As the pulley turns, friction at the axle exerts a...
  42. G

    Acceleration of strings in two pulley systems

    Hi anyone, I'm confused about the magnitudes of the acceleration of the two objects here: It's been awhile since I try to find the answer on internet, I've found numbers of different answers, so I'd like to know if anyone could help me.. In my imagination, if the bigger object moves by...
  43. X

    Calculating Speed of Falling Mass on Pulley System

    Homework Statement A string is wrapped tightly around a fixed pulley that has a moment of inertia of 0.0352kg/m2; and a radius of 12.5cm. A mass of 423g is attached to the free end of the string. The mass is allowed to fall under the influence of gravity. As the mass falls the string causes the...
  44. S

    I with Ramp and Pulley Physics Problem

    Homework Statement The suspended 2.2 kg mass on the right is moving up, the 2 kg mass slides down the ramp, and the suspended 8.9 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 and...
  45. H

    Pulley problem with moment of inertia

    Homework Statement A 28.5 kg block (m1) is on a horizontal surface, connected to a 6.10 kg block (m2) by a massless string. The frictionless pulley has a s R = 0.087 m and a moment of inertia I=0.140 kgm2. A force F = 231.3 N acts on m1 at an angle theta = 30.5°. There is no friction between...
  46. R

    Stepped Pulley: Angular and Linear Acceleration

    A stepped pulley is essentially a system of connected cocentric disks that have different radii. A stepped pulley (I= 2.0 kg*m^2) is placed on a frictionless axle and then strings are attached to two radii of 20 and 50 cm. The other ends of the strings are attached to a 2.0 and 1.0 kg mass...
  47. B

    Frictional Torque for Static Equilibrium of a Pulley

    Homework Statement A mass of 0.311kg is attached to one end of a string, and a mass of 0.625kg is handing off the other end. The string goes over a pulley which has friction in its axle. What is the magnitude of frictional torque required to maintain static equilibrium? Homework...
  48. A

    Does T3 Equal the Sum of m1g, M2g, and Mpg in a Frictionless Pulley System?

    Homework Statement A pulley with mass Mp and a radius Rp is attached to the ceiling, in a gravity field of 9.81 m/s2 and rotates with no friction about its pivot. Mass M2 is larger than mass m1. T3 holds the pulley. The quantities Tn and g are magnitudes. (Select T-True, F-False, G-Greater...
  49. M

    Conservation of Energy within a pulley system

    Homework Statement Two objects are connected by a light string passing over a light frictionless pulley as shown in the figure. the 5.87 kg object is released from rest at a point 2.55m above the floor. The acceleration of gravity is 9.8 m/s^2. What is the speed of each object at the instant...
  50. J

    Rotational Dynamics involving a pulley, spring, and block

    Homework Statement A block of mass m = 9.00 kg is situated on an incline of angle θ = 51.0^{\circ} with coefficient of kinetic friction \mu_k = 0.200, and is connected to a light spring of spring constant k = 40.0 N/m via a light rope passing over a massive pulley as shown. The block is...
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