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. karush

    MHB Angular speed of 2 pulleys on a belt

    two pulleys connected by a belt have 15cm and 8cm radius The larger pulley rotates $25$ times in $36$ sec, Find the angular speed of each pulleey in radians per second. the 15cm pulley has circumferce of $30\pi$ so $\displaystyle\frac{25\text { rev}}{36 \text {sec}} \cdot\frac{30\pi\text{...
  2. G

    Forces in Pulleys: Gr 12 Physics Help for Gary

    Homework Statement https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-prn2/v/1234318_630176667033105_887013223_n.jpg?oh=0197e43e2263a6cffc784ffa9e6da3b0&oe=5244B77F&__gda__=1380228307_39b71a04cd5c0b63205a9b7139f9a620 hey guys, I managed to take a picture of the problem. I am in gr 12...
  3. E

    Multiple Pulleys and Multiple Weights Problem

    1. Homework Statement Solve for T (The force required to keep the pulleys at equilibrium) See attached image for pulley setup. 2. Homework Equations W2>W1 N=mg 3. The Attempt at a Solution Currently I have drawn out all the forces that act on each pulley, and I know there...
  4. A

    How Does Block 1's Acceleration Compare to Block 2's in a Dual Pulley System?

    In the figure below, the pulleys and the cord are light, all surfaces are frictionless, and the cord does not stretch. http://awesomescreenshot.com/0301qqz07c How does the acceleration of block 1 compare with the acceleration of block 2? (Use the following as necessary: m1, m2, and a2.)...
  5. 0

    Static Equilibrium Two Pulleys and Weights With Ring

    I have a problem. Lets say there were two pulleys put at equal height. You have a metal ring and attach three wires to it. At the end of each wire, have three weights of mass w. One weight hangs down, one weight goes over one pulley and the other over the other pulley. The system goes to...
  6. D

    System of two inclines planes and pulleys

    The diagram shows two particles, A of mass 5m and B of mass 3m, connected by a light inextensible string which passes over two smooth, light, fixed pulleys, Q and R, and under a smooth pulley P which has mass M and is free to move vertically. Particles A and B lie on fixed rough planes inclined...
  7. P

    What is the Angular Momentum of a System with Pulleys and Blocks?

    Homework Statement A block of mass m1 is attached to a block of mass m2 by an ideal rope passing over a pulley of mass M and radius R as shown. The pulley is assumed to be a uniform disc rotating freely about an axis passing through its center of mass (cm in the figure). There is no friction...
  8. J

    Three masses, pulleys, dynamics, and tension (Please help)

    Homework Statement there are three masses m2 is on a table top with coefficient of friction of 0.350 with two different masses on each side. They are connected by a mass-less string and friction-less pulley m1=4kg m2=1kg m3=2kg 1.]find the acceleration of all three masses...
  9. N

    How do lever arms affect the velocity of objects?

    I need help with this attached question! The answer is supposedly B because of something to do with lever arms. But I don't get it at all!
  10. andyrk

    Conditions for pulleys and strings

    Homework Statement Why are pulleys frictionless and massless in the pulley questions? What would happen if they are not frictionless and not massless? Why are the strings connecting the blocks in pulley questions massless and inextensible? What would happen if they are not massless an not...
  11. T

    Does a Double Pulley System Double the Stretch Distance of a Spring?

    I know in a double pulley system, the rope moves twice the distance of the load. What about a system such as this? Would the stretch distance of the spring be twice the moved distance of the load? I'm having trouble visualizing these things. Thanks!
  12. S

    Need help, mechanics problem with pulleys and tensions

    I've already tried this problem but yielded an impossible answer: Homework Statement We have a pulley with a mass-less rope attached to two masses hanging off each side of the pulley: -m1 (4kg), suspended 1m off the ground -m2 (2kg), on the ground The mass (M) of the pulley is 2.6...
  13. Saitama

    Pulleys and Blocks: Solving Homework Equations

    Homework Statement (see attachment) Homework Equations The Attempt at a Solution Case a) i)F=160N F is enough to overcome the static friction acting on block ##m_1##. Hence during motion kinetic friction acts and due to Newton's third law, an opposite and equal force acts on...
  14. Saitama

    Pulleys and Springs Homework Help

    Homework Statement (see attachment) Homework Equations The Attempt at a Solution At equilibrium conditions, the forces acting on ##m_2## are the tension due to the strings and its weight. ##T=m_2g+T'## where T is the tension in the string above ##m_2## and T' is the tension in the...
  15. R

    Help settle an argument Mass system on frictionless pulleys

    Homework Statement I got into a disagreement with a fellow student today. He insisted that it's possible to simplify the system on the right as the system on the left. I agree with him that the difference in potential energy (and, therefore, the kinetic energy) is the same but I insist that...
  16. H

    Confusion about tension and pulleys

    Homework Statement I am a little confused about the concept of tension as it relates to pulleys. I am studying torque right now, and it says in the textbook that the tension in the rope around a pulley produces a torque that causes the pulley to turn. I don't fully understand this. I thought...
  17. M

    A Question About Pulleys and Spring Scales

    Homework Statement The question shows two 5kg masses at rest hanging from two pulleys on opposite ends of a table. The string is massless and the pulley is frictionless. Homework Equations They want to know what the spring scale reads (in the middle of the masslessstring). The...
  18. M

    What is the tension in a system of 2 pulleys when acceleration is 0?

    Homework Statement Calculate the tension T in case a, b, and c if acceleration = 0. Ws = weight of the bottom pulley W = weight of the weight Homework Equations mg - T = m*a The Attempt at a Solution For a, it just seems like T = Ws + Wm since the bottom pulley is connected to...
  19. B

    Tension in Fixed Pulleys: Understanding Forces and Equilibrium

    Homework Statement http://learn.uci.edu/media/OC08/11004/OC0811004_L6Pulley.gif Homework Equations The Attempt at a Solution OK so I am a bit confused about how pulleys work. Assume the pulley in the diagram is massless and frictionless and that ropes/hinges are massless. Now...
  20. L

    Solve Pulleys & Mass Homework: Lift 60N Box w/ 3 Pulleys

    Homework Statement A man is trying to lift a box using three pulleys and two peices of rope. Each pulley can turn without friction and has negligible mass.The first rope, attached to the man, paases down under pulley A, up over pulley B and down to the frame of pulley C. The second rope is...
  21. S

    Force with friction, pulleys and cords

    Homework Statement Homework Equations F=ma fk=μR The Attempt at a Solution What's wrong in my work? Is a(B) not equal to a(A)? Why?
  22. P

    Three Pulleys 3 masses, find tension

    Homework Statement Three objects mI. m2 and m3 are suspended from three massless and frictionless pulleys as shown in the diagram. ml is 6 kg, m2 is 2 kg and m3 is 3 kg. Find the tension of the string when the system is set in motion (i.e. all masses are moving). Answer in N Options are: (a)...
  23. C

    Finding acceleration of a mass being pulled by another mass over two pulleys

    Homework Statement A mass m1 is pulled along a frictionless horizontal surface by a rope of tension T1, which passes over a pulley of mass mP1 to a hanging pulley of mass mP2, after which it is fixed to the ceiling, as shown in Fig. 1. Labeling the tension between pulleys 1 and 2 T2, and that...
  24. P

    Calculating Acceleration and Tension in a Rope and Pulley System

    Homework Statement An environmentally-sensitive daredevil wants to use a large mass, a rope, and a pulley to accelerate toward ramp while his motorcycle is in neutral, as shown below. If friction is negligible, what will the acceleration of the motorcycle be and the tension of the rope...
  25. C

    Wordy Physics on Forces, Pulleys, and Friction

    Hi. I'm new here, and decided to sign up now that physics is actually difficult for me in first year university... Hope to find the help I need, and help those that I can. Anyway.. I'm having trouble with these wordy physics problems... 1) A light rope passing over a light frictionless pulley...
  26. L

    For part b, I am lost.Multiple Pulleys: Solving Physics Problems

    Multiple Pulleys! Homework Statement A 60 kg mass and a 10 kg mass are attached together by massless inextensible strings which pass over light frictionless pulleys. One pulley is free to move while the other is fixed. a) The system is initially held at rest by means of a force supporting the...
  27. L

    3 weights suspended on 2 pulleys to form a M shape

    Homework Statement A block with a mass of 25 kg is hung midway between two pulleys, with a rope connecting a hook at the top of the block to each of the two pulleys. On the other side of the pulleys, both ropes are connected to blocks with masses of 15 kg. The 25 kg mass in the middle sags...
  28. L

    Three blocks suspended on 2 pulleys to form a M shape

    Homework Statement A block with a mass of 25 kg is hung midway between two pulleys, with a rope connecting a hook at the top of the block to each of the two pulleys. On the other side of the pulleys, both ropes are connected to blocks with masses of 15 kg. The 25 kg mass in the middle sags...
  29. K

    Can we write equations for strings in pulley systems?

    Ofcourse we can write the equations for blocks on a single fixed pulley taking the tension upwards and weight as downwards and then equating according to the acceleration. Can we write equations for the string (massless or with mass)?
  30. P

    Pulleys and Mass becoming infinitely large

    This is 2 problems that continue one another; I solved the first one but do not understand the second. Homework Statement A 100kg man dangles a 50kg mass from the end of a rope. If he stands on a frictionless surface and hangs the mass over a cliff with a pulley, the tension in the rope will...
  31. B

    3 Pulleys System, find the acceleration of both mass.

    Homework Statement Here is a picture that I putted together(see attached picture). m1= 0.235 kg N = m1g = 2.303 N m2= 0.350 kg m2g = 3.430 N fk= 0.590 N By measurement, I confirmed (d1)=4(d2). Therefore, (v1)=4(v2), a1= 4(a2). Homework Equations ƩFx=(T1)-fk=(m1)(a1)...
  32. V

    Pulleys: Why would my calculated work output be higher than my work input?

    Homework Statement The experiment in my Physics lab today was to determine the mechanical advantage and efficiency of various pulley systems. My calculated work output is higher than my work input, which is causing an abnormally high value for efficiency, and I am attempting to find the source...
  33. W

    Multiple Pulleys and Masses with Friction

    Multiple Pulleys and Masses with Friction (Picture Included) Homework Statement http://content.screencast.com/users/Waraa/folders/Snagit/media/2d699ba1-32e0-4d9c-b79f-1a1d85dccd12/03.19.2012-15.49.46.png I have solved the question but I am still iffy as to whether my solution is correct...
  34. W

    Two Pulleys with two acceleration and two tensions (Diagram included)

    pulley Homework Statement Two masses are attached together by means of light inextensible strings and light frictionless pulleys as shown in the diagram. The system is released and the upper block slides along the table. The coefficient of friction between this block and the table is 0.32...
  35. P

    Block on inclined plane with pulleys and friction

    Homework Statement coefficient of kinetic friction = 0.15 Find the acceleration of block a. Homework Equations see below The Attempt at a Solution http://www.wolframalpha.com/input/?i=-200sin30%2B0.15*200cos30%2B2x%3D-200%2F32.2*a%3Bx-40%3D40%2F32.2*b%3Ba%3D0.5*b I used x for...
  36. N

    How can pulleys or levers multiply forces?

    Can anybody please tell me how pulleys and levers multiply forces without using ideas such as input power(or work)= output power(or work), torque etc. I can't understand the basic mechanism behind it. Please check out my doubt attached to this thread as a bmp image.
  37. C

    Gears, Pulleys, & Electric Motor Questions

    Hi all, brand new to the forums. I'm a student of chemistry so I am very unknowledgeable about mechanical engineering and need some help. Not asking for spoon-feeding. What I am trying to accomplish is fairly simple(I hope). I would like an electric DC motor to turn a 1in diameter teflon...
  38. D

    Question on pulleys and tension

    Homework Statement Two objects of masses m1 and m2 are connected via a massless string and ideal pulleys. The coefficients of friction between m1 and the horizontal surface are ms and mk a) what condition needs to be met to set the system in motion? b)assuming that this condition is (barely)...
  39. G

    Newton's Law, tension, blocks, pulleys at an angle, friction

    Hi all, I'm really stumped at this question five of my assignment. Could anyone please give me some help? I don't even know where to start. Thanks
  40. A

    Pulleys moving down with constant speed

    Homework Statement Please refer diagram attached. The pulleys are moving down with constant speed u each. Pulleys are light , string ideal. What is the speed with the mass moves up? Homework Equations The Attempt at a Solution Now, I got the answer as ucosΘ, obviously...
  41. L

    How Do You Solve Truss Reactions and Pulley Accelerations?

    Homework Statement For the truss find the reactions at point A and B. For pulley, find the relation bet acc of A and block B. Homework Equations The Attempt at a Solution For the truss, take moments at B. F212 + NA12=F110 NA=-2kN which is wrong. Where did I go wrong? ans is...
  42. B

    Belts and pulleys for WIND TURBINE ?

    Belts and pulleys for WIND TURBINE ? Hi, I have been working on a Vertical Axis Wind Turbine. The blades I am able to fabricate produce more torque than speed. I am adding a synchronous belt drive transmission. The current configuration is 1 rpm at the input and 7 rpm at the output. I have...
  43. Q

    What is the Velocity of Point P in a Multiple Pulleys System?

    Homework Statement The block B moves to the right with a constant velocity of 30 cm/s. Given this, which of the following is correct: 1. Speed of block A is 15 cm/s 2. Speed of point P is 60 cm/s 3. Speed of point P is 30 cm/s 4. Speed of block A is 40 cm/s Homework...
  44. B

    Acceleration of two pulleys help

    Homework Statement If a1 and a2 are the accelerations of m1 and m2, respectively, what is the relation between these accelerations? Homework Equations Link to the diagram : http://www.webassign.net/serpop/p4-38.gif The Attempt at a Solution The answer is a1 = 2*a2, but I'm having trouble...
  45. 1

    Understanding Pulley Systems: Forces on Blocks with Unequal Mass

    Homework Statement I can do the math work, but I always overthink these multiple choice concepts. A block is attached to each end of a rope that passes over a pulley suspended from the ceiling. The blocks do not have the same mass. If the rope does not slip on the pulley, then at any...
  46. A

    Pulley system: 2 pulleys and 3 mass

    Homework Statement Note: My textbook and first language is french, I am sorry if I mistranslated some terms. A friction-less rope goes around the fix pulley A. At one side of the rope, there is a mass M1. On the other side, there is a pulley of mass M2. Another friction-less rope goes...
  47. S

    Kinetic frictions, pulleys, and Newton's third law

    Homework Statement Block A and B are connected by a string passing over an essentially frictionless pulley. (Block A is on a horizontal plane, while block B is suspended in the air) When the blocks are moving block A experiences a force of kinetic friction of magnitude 5.7N. If mA= 2.7kg and...
  48. R

    Two pulleys and same masses - velocity?

    Homework Statement If two equal masses are suspended as in the following, and they are both initially at rest, after they are released, what is the velocity of the leftmost mass at the instant the separation between the two masses is h ? Assume frictionless pulleys and extensionless strings...
  49. I

    Pulleys and weights - finding acceleration and tension

    Homework Statement A 24 kg block with a pulley attached slides along a frictionless surface. It is connected by a massless string to a 6 kg block via the arrangement shown. The acceleration of gravity is 9.81 m/s2 . The first part wanted you to find the horizontal distance traveled by the...
  50. D

    Loads using pulleys in a deflection test apparatus.

    I am desiging a simple deflection test apparatus for my company. In the system I am using a few pulleys, a steel cable, a force gage, and a ratchet strap. I want to use the ratchet strap as opposed to dead weights so I can apply varying amounts of force to the test member. My question...
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