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

    Pulleys - Relationship between mass and aceleration

    1. Homework Statement 2. Homework Equations How to get ax=2ay? 3. The Attempt at a Solution a=10m/s2 And the solution I found was a=2m/s2 I found this at : http://www.physicstutorials.org/home/exams/dynamics-exams/142-dynamics-exam1
  2. S

    Solve Broken Leg & Pulleys: Find Weight W

    Homework Statement assume that the total downward force exerted at A & B by the leg is 38N. find the weight W, attached on the lower puller Homework Equations please see attached diagram The Attempt at a Solution [/B] i have written roman numerals to help determine which equation refers to...
  3. B

    The double Atwood machine has frictionless, massless pulleys

    Homework Statement The double Atwood machine has frictionless, massless pulleys and cords. Determine (a) the acceleration of masses ma, mb, and mc, and (b) the tensions Fta and Ftc in the cords. Homework Equations F=ma The Attempt at a Solution So I drew free body diagrams for the mass A...
  4. J

    Torque: Two pulleys wheels connected by a belt

    Homework Statement Ok, so first I find the tension on the top portion of the belt.. 3.0=T(100/1000) , T-> tension T=30N , though I'm not sure if taking the diameter of Q is correct. Then I find the torques on wheel P, which I multiply the tension with the radius (150/2 mm) which I get 4.5 Nm...
  5. K

    Weights and pulleys in harmonic motion

    Homework Statement No friction. m3=5m, m2=12m, m1=3m Prove that the system's acceleration when it's released is a=0.2g. is it the max acceleration? Show that the equilibrium point is at x0=0.75L Show that the kinetic energy of the system is E=mgL Show that m2 will stop momentarily at...
  6. K

    Throwing 1Kg the highest without electronics

    hello everyone. me and my mates as some fun over the school holidays are having a competition to see who can throw 1Kg the highest without the use of electronics due to an unfair advantage to those more well off etc. my first idea was a rail gun but as that requires electronics it is unable to...
  7. K

    Pulley project of mine requiring help

    text is same as on pic. I'm trying to express this diagram as algebraically as possible so later on I can add real world limitations into my equation and see what other requirements are needed. I got the first and simplest one which is to be in equilibrium the mass/weight of B has to be...
  8. K

    Pulley question -- 2 pulleys and 2 weights

    THIS THREAD WAS INCORRECTLY PLACED IN THE CLASSICAL PHYSICS FORUM, SO THERE IS NO TEMPLATE Hi, everyone. my teacher stuck me with these questions and i am need of a little help answering question 2. here's my answers to question 1 first. 1a) a=0, as system would be in equilibrium when F=0 b)...
  9. graceless9

    Mechanism to move a platform at a constant velocity

    Hi all, I'm new here on Physics Forums and can't wait to delve into some juicy topics! I have a very practical problem that I need help with. I am doing a home project where I want to move a platform on wheels (loaded to a maximum of 70kg) in a 1.5m long straight line across the floor at a...
  10. MironeDagains

    Why Do My Pulley System Calculations Differ From My Teacher's Measurements?

    Homework Statement There's a 200g piece of weight hanging by a string. That string is then split into two strings, each at θ from the horizontal and Φ from the horizontal. These two strings are each connected to force sensors which measure their tension in Newtons. I know how to do this...
  11. Puddles

    Atwood Incline Pulley problem with two pulleys

    Homework Statement Given that a weight m1 is attached to a string going over a perfect pulley attached to another pulley suspending weight m2, and that weight m1 is on an incline with an angle of 37 degrees, find acceleration, tension, which mass hits the ground first, time needed to hit the...
  12. M

    MHB Exploring the Physics Behind Fixed and Movable Pulleys

    Hey! :o Fixed pulley: $$F_G \cdot r=F_z \cdot r \Rightarrow F_G=F_z$$ Only force transfer, no changement of force Movable pulley: Like one-sided lever, current center of rotation is at the circumference of the pulley: $$F_G \cdot r=F_z \cdot 2r \Rightarrow F_z=\frac{F_G}{2}$$ Could you...
  13. SpacemanRich

    Newton's second with Pullys, Ropes, and Boxes (Frictionless)

    Homework Statement [/B]In the drawing, the rope and the pulleys are massless, and there is no friction. Find (a) the tension in the rope and (b) the acceleration of the 10.0-kg block. (Hint: The larger mass moves twice as far as the smaller mass.) 2. Formula's Used. F = ma, W = Mg. The...
  14. S

    Two Weighted Pulleys with a Suspended Mass

    Homework Statement Consider a uniform 10-kg circular disk with diameter .4m. The disk is free to rotate about a horizontal axis through its center. A (massless) cord wrapped around the disk passes over a 2-kg pulley, P, with diameter .2m and is attached to a 25-kg mass. The pulley's mass...
  15. C

    Calculating Tension in Friction & Pulley: Solving for a=3 m/s^2

    1. If flat car is given an acceleration a = 3 m/s^2 starting from rest, compute tension (in N) in the light inextensible string connected to block A of mass 30 kg. Coefficient of friction between block and flat car is = 0.50. Neglect mass of pulley and its friction. Take g = 10. 2. Friction...
  16. S

    Statics: find tension/wrap angle for pulley

    Homework Statement Given: T(sub-B) plus T(sub-B) prime = 36. Both T(sub-C) values are 0. T (sub-D) =36 and T (sub-D) prime = 12. Find values of T (sub-B) and T (sub-B) prime[/B]Homework Equations OK, so we need to find the wrap angle, which should be 180 + 30 -22, which comes to 188...
  17. B

    What is the tension in a rope supporting multiple weights using a pulley system?

    Homework Statement A 100 kg man dangles a 50 kg 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 be: (A) 250 N (B) 333 N (C) 500 N (D) 667 N The answer is B but I am having a difficult time setting...
  18. P

    How Do You Calculate Acceleration in a Two Mass, Two Pulley System?

    Homework Statement Masses ##M_1## and ##M_2## are connected to a system of strings and pulleys as shown (I have attached an image). The strings are massless and inextensible, and the pulleys are massless and frictionless. Find the acceleration of ##M_1##. Homework Equations $$\sum_{}^{} F_y...
  19. G

    Forces with Tension and pulleys

    Homework Statement I had a set of old concrete steps, with a mass of about 2.5 metric tonnes (i.e., 2500 kg), which needed to be dragged across the yard. One way to make the job easier was to rig a block-and-tackle, which consisted of two pulleys. I used a thick rope to tie one pulley to the...
  20. P

    How to Calculate Power Transmission in a V-Belt Pulley System?

    OK, struggling a little here to grasp this one. Any help guiding me in the correct direction would be welcome. 150mm diameter pulley is directly driven at 250 rev per min. A V-belt is used to transmit power from this electrically driven pulley to another, which is 400mm in diameter. The centre...
  21. Valerie Prowse

    Find mass of cylinder (rotational motion question)

    Homework Statement A light string is wrapped around a solid cylinder and a 300 g mass hangs from the free end of the string, as shown. When released, the mass falls a distance 54 cm in 3.0 s. a. Draw free-body diagrams for the block and the cylinder. b. Calculate the tension in the string...
  22. Feodalherren

    ME Dynamics - Multiple ideal pulleys + an inclined plane

    Homework Statement Find the acceleration of both blocks Homework Equations Dynamics The Attempt at a Solution Everything in black is given in the problem. The red/blue is my work. First I want to relate the acceleration of block A to block B by finding the constraint equations: Lrope = 2L1...
  23. hdp12

    Problem Check: Equilibrium of Particles

    Homework Statement A continuous cable of total length 4 m is wrapped around the small pulleys at A, B, C, D. If each spring is stretched 300 mm, determine the mass m of each block. Neglect the weight of the pulleys and cords. The springs are unstretched when d=2 m. The Attempt at a Solution I...
  24. terryds

    Understanding the Velocity and Acceleration of Blocks Linked by Multiple Pulleys

    Homework Statement http://www.sumoware.com/images/temp/xziltxnrjlckqjqs.png Two blocks ( A and B ) are linked by rope through three identical pulleys C, D, and E. Pulley C and E are in stationary, while D is pulled down so its constant velocity 1 m/s If vA = 4m/s when A goes down 2 m...
  25. M

    Find Theta & Mass of Box Using Forces & Pulleys

    Homework Statement Note that the vector F is 50N. I need to find Theta and the Mass of the Box(M). http://i5.minus.com/ib08xMuKZxTSbc.png Homework Equations What I have so far: Pulley 2: FY: T2cos(20) - T1sin(60) + Fsin(45) + T2sin(30) = 0 FX: T2sin(20) + T1cos(60) + Fcos(45) - T2cos(30) =...
  26. J

    Pulleys with Strings Having Mass

    Suppose there is a pulley (a disc) of mass m1 and a string passes over the pulley with masses m2 and m3 hanging on both ends of the string with m3 > m2. I know that the acceleration should be (m3 - m2)g/(1/2m1 + m2 + m3) and I know how to get there. However, since the pulley rotates and has...
  27. J

    Question On Effects of Changing Criteria Of Pulleys

    1.What would be the effect of the following factor on the maximum power that can be transmitted. (give reasons for your answers) Increasing the included angle of the pulley groove. 2. What would be the effect on the following if the load torque is increased and the speed maintains constant? The...
  28. B

    Solving a Physics Problem: Large Weight Over a Building

    Homework Statement A large weight hangs over the side of a building from a cable. The cable goes over a pulley to a horizontal roof and is attached to a small weight of half the mass. The coefficient of sliding friction between roof and the small weight is 0.5. What is the approximate...
  29. B

    Confused conceptually about work done with pulleys

    Hello, I am confused about a problem regarding work done and pulleys. I am confused mainly by the last two, but not 100% confident in the first two either. 1. Homework Statement Two blocks are connected by a very light string passing over a massless and frictionless pulley (Figure 2). The...
  30. Calpalned

    Confusion over the reduction of force for pulleys

    Homework Statement A window washer pulls herself upward using the bucket-pulley apparatus shown in the figure. How hard must she pull downward to raise herself slowly at constant speed? The mass of the person plus the bucket is 71kg . Homework Equations F of gravity = mg F effort = mg/2 The...
  31. B

    Help with Pulleys: Weight on Anchored Rope?

    So I have started a conundrum with a question about pulleys. There is one pulley anchored and suspended from a ceiling. There is a 100 pound weight suspended on one pulley and the other end of the rope is anchored to the ground. The question is how much weight is on the pulley? 50 pounds, 100...
  32. SteliosVas

    What is the solution for a pulley system with 200N weight and 40N weight?

    Homework Statement Pulley system, attachment below. Would be impossible to explain without a diagram. Homework Equations Wa = 200N Va0=2m/s t= 2 seconds Wb= 40N μK=0.2 g=9.81m/s^2 The Attempt at a Solution Okay my attempted solution was this: For block A: 40N +...
  33. K

    Laws of Motion (Pulleys, blocks)

    Homework Statement A truck shown in the figure is driven with an acceleration a =3m/s2. Find the acceleration of the bodies A and B of masses 10 kg and 5 kg respectively, assuming pulleys are mass less and friction is absent everywhere. The Attempt at a Solution I have written three...
  34. A

    How Do You Calculate Tension in a Frictionless Pulley System?

    1. Homework Statement Calculate the tension in the cable connecting the two masses. Assume all surfaces are frictionless. http://tinypic.com/r/20jg36s/7 2. Homework Equations 3. The Attempt at a Solution I tried to begin the solution but came out with a negative acceleration...
  35. C

    Solve Work w/ Pulleys Homework: Answer & Explanation

    Homework Statement A force F is used to raise a 4-kg mass M from the ground to a height of 5 m. What is the work done by the force F? (Note: sin60 = 0.87; cos60 = 0.5. Ignore friction and the weights of the pulleys.) A) 50 J B) 100 J C) 174 J D) 200 J...
  36. R

    Speed difference in the pulleys in a block and tackle setup

    I am designing a block and tackle system (because I can't think of anything more simple) to take up the slack in a loop of cordage for a machine I am tinkering on. The loop only travels in one direction due to a set of cam cleats. I am trying to figure out if all the pulleys in a block need...
  37. jbunniii

    Masses on table - Acceleration of Connected Objects

    Homework Statement This is problem 2.9 from Kleppner and Kolenkow, 2nd edition. I think I got it right, just want to check since I'm self-studying. Masses on table Two masses, ##A## and ##B##, lie on a frictionless table, as shown (see my crudely drawn figure in the thumbnail :tongue:). They...
  38. jbunniii

    2 masses, 2 pulleys, 2 ropes

    Homework Statement I am teaching myself mechanics using Kleppner & Kolenkow, second edition. My background is in math, so I don't need assistance with that aspect, but my physical intuition is weak/nonexistent. :tongue2: This is problem 2.8. Masses ##M_1## and ##M_2## are connected to a...
  39. G

    Pulleys: One mass hanging between two other masses

    Homework Statement Explanation: There are three masses in this problem. Two masses are sitting on two opposite surfaces. These surfaces have a space in between them, where a third mass is hanging down. These masses are connected by a continuous pulley system. μ = 0. The question asks...
  40. G

    Three hanging masses and two pulleys, why does m3 accelerate?

    Homework Statement Figure CP7.57 shows three hanging masses connected by massless strings over two massless, frictionless pulleys. a) Suppose: m1 = 2.5 kg, m2 = 1.5 kg, and m3 = 4.0 kg. Find the acceleration of each. b) The 4.0 kg mass would appear to be in equilibrium. Explain why it...
  41. ShayanJ

    Degrees of Freedom & Constraints of Pulley & Spring System

    Consider the system shown in the picture. http://updata.ir/images/m9wcnahubdfanhq9edok.jpg What are its degrees of freedom? And is the Lagrangian below,the correct one for this system? \mathfrak{L}=\frac{1}{2} M_2...
  42. B

    Increasing the number of pulleys

    Homework Statement I'm trying to do a lab and none of my data is making sense. It's making it very difficult for me to draw conclusions and make sense of the post-lab questions with the data I have. Here are the questions I am struggling with: 1. What happens to the force exerted as mechanical...
  43. G

    Tension and Pulleys Cannot understand this problem

    Tension and Pulleys...Cannot understand this problem So this is NOT for homework, (I'm doing practice problems reviewing for a final), but this is a textbook question that might as well be homework. This is the question: Figure 5-53 shows a man sitting in a bosun’s chair that dangles...
  44. 9

    Two pulleys (one is a combination of two cylinders), and hanging mass.

    Homework Statement Two pulleys are mounted on fixed axles that have negligible friction. The small pulley has a moment of inertia of 9.0 kgm^2, and is made of up of two cylinders wielded together, one of radius 7.0 cm, and one of radius 15.0 cm. The large pulley has a radius of 41.0 cm, and a...
  45. F

    Angular momentum and pulleys

    Homework Statement In the graph shown in the picture, an expression for the acceleration of the pulleys is obtained. Homework Equations The Attempt at a Solution The thing i don't understand is, how do we find the angular momentum for the system? In class, I was told that the angular...
  46. J

    Pulleys with inertia and friction

    Homework Statement http://essbaum.com/images/Pulley_diagram.png We have a bonus question where we are asked to find the mass of ##m_{1}## necessary to accelerate ##m_{2}## upward at ##1g##, and we have to include friction in the pulley bearings as well as the pulley inertias. The...
  47. J

    Why Does Tension Vary on Different Sides of an Accelerating Pulley?

    Sometimes when I see pulley and rope questions people will say "for a non-extensible rope the tension is uniform throughout the rope". But I am now learning pulleys and rotational inertia and it seems to be necessary to consider the rope on either side of a pulley to have _different_ tension if...
  48. F

    Pulleys & Forces Homework: Struggling to Understand

    Homework Statement Hey guys I'm really having problems understanding this despite looking at the solution, which is fully laid out here: http://iweb.tntech.edu/murdock/books/v1chap4.pdf I know that m2 moves twice the distance that m1 moves. I have tried looking at each rope as a...
  49. Z

    Forces on frictionless pulleys

    [b]1. A mass m1 is attached to a second mass m2 by a rope that goes over a frictionless and massless pulley. Mass m1 is being pushed down a rough inclined plane with force F. The Angle of the incline is θ1, the force pushing m1 is acting at an angle θ2 . and the coefficient of kinetic friction...
  50. karush

    MHB Linear and angular velocity of 2 pulleys and a belt.

    A belt contects two pulleys with radii $\displaystyle5\text { in}$ and $3\text { in}$ the $\displaystyle5\text { in}$ pulley is rotating at $\displaystyle\frac{1000\text{ rev}}{\text{min}}$ What is the linear $\displaystyle\text{v}$ in $\displaystyle\frac{\text{ft}}{\text{sec}}$ of the belt...
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