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. P

    Analyzing Forces in a Platform and Pulley System

    A girl stands on a platform and pulley system. The masses of the platform, girl and pulley are M, m and u respectively. The rope is mass-less. Let the girl pull up on the rope so that she accelerates a upwards. What is the tension of the rope? What is the normal force between the person and the...
  2. J

    Solving for different masses in pulley system with KE

    Homework Statement So I am stuck on this homework problem. I understand the general direction I have to take, but my algebra and physics aren't good. Here's the problem: A simple Atwood's machine uses two masses, m1 and m2. Starting from rest, the speed of the two masses is 10.0 m/s at the end...
  3. Wayland Bugg

    Rope tangent angle over pully given position of offset load

    I am trying to symbolically resolve the angle of rope that suspends a load (rectangle) between two pulleys given the length of rope that is let out over the pulleys. See attached image. the load is not intended to move horizontally, only vertically. so you can imagine each pulley must have an...
  4. terryds

    Pulley Problem (with force upward)

    Homework Statement http://www.sumoware.com/images/temp/xzstefmnkmsctpxh.png A man pulls up a pulley shaft with force F (see the picture above) Assume that the pulley and cord have no mass, and the mass of object 2 is bigger than the mass of object 1. a) Determine the maximum normal force to...
  5. B

    Acceleration of massless pulley and blocks

    Homework Statement Consider a situation I'm curious why is that the massless pulley's acceleration is just the avarage of acceleration of m1 and that of m2? ab=(a1+a2)/2 Homework Equations Forces acting on pulley are Tc-2Ta=0 (because pulley is massless, force can't give it acceleration)...
  6. A

    How Does Tension in a Pulley System Account for Static Friction?

    Homework Statement Homework Equations us*Fn = Fs FNET = ma Fk = us*Fn 3. The Attempt at a Solution A 0.42*9.8*4.4 = Fs Fs = 18.1104N B F = ma m = 18.1104N/9.8m/s/s m = 1.848kg 1.848kg-0.120kg = 1.728kg for the washers to make up for 1.728kg/(0.02kg/washer) = ~86 washers C I'm not sure...
  7. H

    Solving 3 Block and Pulley Homework

    Homework Statement A block of mass m1 is on top of a block of mass m2. Block 2 is connected by an ideal rope passing through a pulley to a block of unknown mass m3 as shown. The pulley is massless and frictionless. There is friction between block 1 and 2 and between the horizontal surface and...
  8. RioAlvarado

    Mechanics Pulley Platform Problem

    Homework Statement Two construction workers each of mass m raise themselves on a hanging platform using pulleys as shown above. If the platform has a mass of 1.2⋅m, the initial distance between the pulleys and the platform is d, and the workers each pull with a force f on the ropes, what is...
  9. B

    Innovative Elevator Design: Pulley & Belt System

    I am designing an elevator system and i wanted to use timing belts with a counterweight. After almost fully completing the design it was brought to my attention that my pulley and belt setup was not the best choice. Any insight on what anyone thinks would be great! The top pulley and belt...
  10. F

    Dynamics Problem -- box accelerated horizontally via a mass & pulley system

    Homework Statement A 1.0 kg box on a horizontal frictionless surface is accelerated by attaching a 1.5 kg mass as shown in the diagram. What is the magnitude of acceleration of the box?(Remember, both boxes accelerate.) Homework Equations F = ma The Attempt at a Solution I drew a free body...
  11. arpon

    Find the Tension and Acceleration of Cable B in Picture 3

    [moderator's note: moved to homework forum so no template] In picture 3, A has touched the ground, so it has stopped. But B has a velocity upward. So in this situation, the cable is not straight. What will be the tension of the cable and what will be the accelertion of B in picture 3 ...
  12. arpon

    Tensions of cable over a pulley

    [moderator's note: moved to homework forum so no template] This is a frictionless ideal pulley. Are T_1, T_2, T_3 equal? If so, why? Please explain in details?
  13. J

    Finding Acceleration in a Pulley and Slope System

    Homework Statement NOTE: This is a problem I found and the question is actually the part B of it. That of ''massless pulley'' I suppose was dealing with the part A (which I don't know what question was), so please don't consider that (:. Homework Equations ##F_{net} = ma## ##\tau =...
  14. J

    Pulley Problem: Keeping boxes stationary on another box

    Homework Statement Homework Equations ##F_{net} = ma## The Attempt at a Solution If ##m_2## accelerates, then the force on this box is ##m_1g## and its acceleration is ##\frac{m_1g}{m_2}##. If I disregard the presence of ##m_1## for a minute, I'll have to push on ##M## with a force such...
  15. N

    Mass Needed to Accelerate a Box Along a Pulley

    Homework Statement Okay, so I am given an acceleration that I need to accelerate a box-thingy, along with a weight inside. Friction is included. I need to come up with a mass that is connected through a pulley to the box. This mass has to accelerate the box at the given acceleration. I am not...
  16. P

    Optimizing Motor Pulley & Rope Combination for High Speed

    Hello Guys, I need little help currently I am working with on a Project that includes Motor Pulley and rope combination. The previous version of our Test bench was having a Motor pulley and rope and the rope was wrapped around the pulley as in most of the cases, but now I am trying to optimize...
  17. J

    Calculating Acceleration in an Inclined Force Problem with Pulley Setup

    I am having trouble on one of my homework problems. The problem is What is the acceleration of the system if M1 is 5 kg and M2 is 4kg and the coefficient of friction between M1 and the table is 0.20? There is an image along with the problem. Basically it is just like a standard inclined plane...
  18. A

    Understanding Forces in a Simple Pulley: Explained with an Image

    As seen in the image below, a hand is pulling one end of a rope that is on a simple pulley, and the object W is pulling another end. What I don't understand is what kind of force acts both objects P and W upward. The downward force is the force of gravity. Since I've learned that these kind of...
  19. C

    Spring Pulley System: Find Max Velocity of Block

    Homework Statement We have a system, consisting of a Disk radius R, with weight M, with a cordless string attached on its edge, at one edge of this cordless string we have a block of mass m, at the other end, we have the string attached to a spring with one end fixed to the floor, with spring...
  20. R

    Effect of friction on the tension in a pulley

    I measure the tension in a pulley system with two masses (one smaller, one larger) where I pull the small mass down and let it go so that the system accelerates in the direction of the larger mass. This is without friction. Then, I try to consider friction. Does the tension in the string...
  21. B

    How does tension affect the motion of a hanging block on a rotating disk?

    Homework Statement This figure shows a uniform disk, with mass M = 2.5 kg and radius R = 20 cm, mounted on a fixed horizontal axle. A block with mass m = 1.2 kg hangs from a massless cord that is wrapped around the rim of the disk. Sample problem 10-8 (has picture diagram and detailed...
  22. W

    Velocity of a block attached to a pulley and cylinder

    Homework Statement A cylinder and pulley turn without friction about stationary horizontal axles that pass through their centres. A light rope is wrapped around the cylinder, passes over the pulley, and has a 3.00 kg box suspended from its free end. There is no slipping between the rope and the...
  23. P

    Algebra of pulley-mass energy equation

    Homework Statement [/B] A 0.20-kg block and a 0.25-kg block are connected to each other by a string draped over a pulley that is a solid disc of inertia 0.50 kg and radius 0.10 m. When released, the 0.25-kg block is 0.30 m off the ground. What speed does this block have when it hits the ground...
  24. M

    Two Masses Hanging on a Massive Pulley problem

    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. The quantities Tn and gare magnitudes. Homework Equations (Select T-True, F-False, G-Greater than...
  25. M

    Upward Acceleration of Hanging Mass Connected Pulley

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  26. O

    Changing masses on an atwood machine

    An example of this kind of a problem would be a frictionless, massless pulley holding two equal masses(say, 5kg each). But then, an additional mass is added to one side (ie, a frog jumping on to mass 1, 1 kg). What would happen to the system? What if the frog jumps off?Initially, I know that the...
  27. N

    Homework Help Pulley, Tension, Mass, Angle

    Homework Statement Using the uploaded picture we have to have a force diagram. And we have to break angled forces into components and indicate which forces are equal with equality. All the masses are up to me (2, 3, 4, 5 kgs) Homework Equations Write an equation for the vertical forces Write...
  28. J

    Centripetal force involved with a pulley system

    Homework Statement If you have a motor pulley and a drum pulley connected by a belt then how do you explain why the belt can sometimes slip if the washing machine is rotating too fast? Homework Equations The Attempt at a Solution I know that the answer involves the tension of the belt being...
  29. E

    Acceleration of a mass hanging from a pulley

    Homework Statement Two blocks, of masses m1 and m2 (with m1<m2) are attached by a massless string of fixed length that runs over a pulley which is free to rotate about its fixed center. The pulley has mass m3, radius r3, and rotational moment of inertia I = (2/3) m3 r3^2 about its center (it...
  30. 2

    Pulley problem: Does the third pulley move up or down?

    Homework Statement ) The pulley system in Figure 1.b consists of two pulleys of radii a and b rigidly fixed together, but free to rotate about a common horizontal axis. The weight W hangs from the axle of a freely suspended pulley P, which can rotate about its axle. If section A of a rough...
  31. T

    Unequal tension of a rope in a pulley system

    I am having a bit of difficulty with the concept of unequal tension in a rope. What are the conditions for unequal tension? I read that the tension is the same when there is no acceleration. Why is this the case? Can someone explain this concept to me? Thanks :)
  32. C

    Calculate Acceleration & Tension of a Pulley System

    Homework Statement Three equal masses are hung from a pulley(2 on one side, 1 on the other). Find the acceleration of the system and the tension between: a) the 2 sides of the pulley and b) between the 2 masses on the same side Homework EquationsThe Attempt at a Solution Got a= g/3, for a) T=...
  33. B

    Minimum Force of 86N to Move Two Blocks

    1. 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 ##\vec{F}##. The coefficient of static friction between all surfaces is 0.63 and the kinetic coefficient is 0.38. What is the minimum value...
  34. Fuichris

    Pulley / Fraying - "Mechanical Flower" Project

    Hi all, "MECHANICAL FLOWER PROJECT" I'm working on a personal hobby art project (non-academic, non-commercial, non-governmental) where I'm mechanizing petals of a plastic flower. Basically, making petals curl open and close. *Please see picture and video. GOAL: To pull continously without...
  35. minimario

    Analyzing a Pulley System: Solving for Energy and Work

    Homework Statement Homework Equations ## W_{nc} = \Delta KE + \Delta PE ## ## PE = mgh ## ## KE = \frac{1}{2} mv^2 ## The Attempt at a Solution For Block B, ## \Delta KE + \Delta PE = \frac{1}{2} 100 v^2 + (-20)(g)(100) ## For Block A, ## \Delta KE + \Delta PE = \frac{1}{2} 50 v^2 + (20...
  36. Hijaz Aslam

    Taking the components of a system containing multiple vectors

    Q.In the arrangement shown in fig. the ends P and Q of an inextensible string move downwards with uniform speed u. Pulleys A and B are fixed. The mass M moves upwards with a speed. ANSWER PROVIDED BY MY TEXT In the diagram ##vcos\theta=u## therefore ##v=u/cos\theta## HOW I TRIED TO DO THE...
  37. D

    Calculating Time for Mass to Travel Distance on a Pulley

    Homework Statement The two blocks in the figure are connected by a massless rope that passes over a pulley. The pulley is 16cm in diameter and has a mass of 1.3kg. As the pulley turns, friction at the axle exerts a torque of magnitude 0.50 N*m. If the blocks are released from rest, how long...
  38. Blake Kopachena

    Keyed serpentine pulley with a 5/8 bore to mount on a motor

    It needs to be 3.0in to 4in OD, the belt which it will drive will have 6 grooves. It will be mounted on a motor shaft and there also has to be a way to tighten it with a screw securely. I am having a really hard time finding one, which is understandable since they are commonly used on...
  39. T

    Finding Tension in a Beam Supported by a Pulley: Solving for Equilibrium

    Homework Statement [Ans: FA = -206i + 188j lb, T = 131 lb] Homework Equations Since it's assumed that the system is in equilibrium, so I assume that ΣF=0 and ΣM=0 The Attempt at a Solution I tried to draw a free-body diagram for the system, and set up three equations below: (I don't know...
  40. D

    Solving Physics Problem 9-72: Angular Speed of Pulley

    1. The problem states: Problem 9-72a: The system shown in the figure below consists of a m1 = 4.24-kg block resting on a frictionless horizontal ledge. This block is attached to a string that passes over a pulley, and the other end of the string is attached to a hanging m2 = 2.12-kg block...
  41. A

    Find the acceleration of a pulley system

    Homework Statement Find the acceleration of the system shown on the image, given m1=0.1kg and m2=0.3kg. Mass of pulleys is to be disregarded, and rope is non-stretchable. Homework Equations m1*a=m1*g-T The Attempt at a Solution I am unsure of how the forces of the second body would act and...
  42. minimario

    Child, Chair, and Spring Scale on Pulley: Forces

    Homework Statement Homework Equations $F=ma$ The Attempt at a Solution (a) Because the spring scale weighs 250 N, the effective weight on the child's side is 230 N. Therefore, $T-230 = \frac{230}{9.8} a$ and $T-250 = -\frac{250}{9.8} a$, so $a = 0.408$. This is correct, but is the...
  43. N

    Velocity of two identical masses over a frictionless pulley

    Homework Statement "Consider the following arrangement of masses. Mass 1 is connected to mass 2 by a very light string and moves over a frictionless pulley so that both masses move with the same speed and move the same distances (m2 to the right and m1 down). Assume m1 = 15 kg, m2 = 15 kg and...
  44. H

    Calculating Mass in Box 3 of a Pulley System

    Question Summarized: The box in the middle is remains motionless; how much mass was placed in box 3? box 1: 35kg middle box: 95 kg box 3: ? kg Attempt at the problem:
  45. M

    Double Pulley Mechanics Problem

    Homework Statement it is a double pulley problem, mass of pulley 1 is 4.1kg, mass of pulley 2 is 6.9kg and mass of crate is 57.2kg. both pulleys are frictionless. the angle at which the rope is pulled is 45deg. What is the minimum tension with which the operator must pull on the cable...
  46. Blake Kopachena

    How can I reduce the speed of my lift without changing its displacement?

    I have a little project, I am building a simple lift that is moved with cable by a 3-phase motor which has it's speed controlled by variable frequency drive. I am going to be implementing PID control into the VFD via PLC that will be based off of a distance reading from an ultrasonic sensor for...
  47. D

    Relationship of acceleration of masses in pulley

    Homework Statement Find the relationship of acceleration between the masses, m1, m2 and m3 where m1>m2>m3. The question has a free pulley in the left attached to mass m1. then goes through a fixed pulley , through a free pulley that is attached to m2 and then through a fixed pulley, with the...
  48. M

    What is the Tension in a Pulley System?

    Homework Statement [/B] 4-31 Homework Equations Tension (Ft) = Force of gravity (Fg) = m × g. The Attempt at a Solution [/B] only manage to reach 60kg x 9.8 = 588N
  49. C

    Frictional Forces: Stacked boxes, pulley with weight.

    Homework Statement The system shown is released from rest. Mass one (0.450 kg) rests on mass two (0.820 kg) and the coefficient of static friction between the two masses is 0.560 and the same for the mass and the table. Determine the maximum mass for M(3) such that mass one will not slide on...
  50. H

    Acceleration in a Multiple Pulley System

    So if you have two masses connected by a massless string in a multiple pulley system as shown below, the acceleration will be different right? I ask because when doing normal pulley problems where two masses are connected by a single thread, you assume the acceleration is equal, though the net...
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