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. jeffrey

    Pulley angular velocity problem

    Further given: - every beam is infinite stiff - pulleys are massless - cables don't stretch, no slip, and frictionless. -Every pulley has a diameter D except pulley Q. Pulley Q has diameter 0.5*D So what I don't understand is how to calculate/determine the velocity at R and S. Can someone help...
  2. F

    Mechanical Advantage of a pulley with horizontal effort

    How will the MA of a fixed pulley change if I apply the effort horizontally? Intuitively, I feel horizontal effort should be lesser effort than vertical effort.
  3. LCSphysicist

    Easy problem about a pulley accelerating

    That is the classic problem involving pulley and masses, I can find everything that is requested, but there is a big problem, i don't know how to justify that the tensions in both side are equal to half of the force.
  4. LCSphysicist

    Differential Pulley: Force to Balance Weight W

    I am trying to deal with this problem, the question is what is the force to balance the weight W, where the rope don't have weight. The bigger pulley at the top has radius a, and the other, attached to the same axis, has radius 0.9a. The force is applied in one side of the freeling rope. I...
  5. LCSphysicist

    Masses, pulley, friction and rotation

    In summarize, i have four equations and five incognits. T2,T1,theta,a2,f Need to find one more equation, but i don't know how
  6. P

    A string over a pulley with two hoops wound like spools on each end

    I have seen the solution to this problem but I don't understand it. Here is my drawing of the problem. Apparently I should do the sum of the forces and sum of the torques for both hoops like this: hoop 1: (1) τ - M1g = M1(a1t-a1R) (2) τR1 = ½M1R12a1r/R1 hoop 2: (3) M2g - τ = M2(a1t+a2r) (4)...
  7. S

    Distance traveled and period of a mass - spring - pulley system

    1. How will the motion of M be? I assume wire S is inelastic so will M move downwards but not in straight line? (I mean M moves downwards but because the left side of pulley is connected to S, it will be static and the right side of pulley can go down along the extension of the spring so its...
  8. H

    Mechanics: Two masses on a pulley causing two cylinders to accelerate

    Hi! I need help with this problem. m1-2-3-4 and R are given. There is no slip in the system. I have to give F1-2-3-4 in respect of the masses and R. Here is what I managed to m1 is easy: m1*a = m1*g - T(tension of the rope) m2: m2*a = T - (?) <-- I have a problem with this. F1 and F3 is the...
  9. cwill53

    What is the relationship between weight and length in a cord and pulley problem?

    I've deduced that the weight of each weight p is half that of the weight P, and likewise P= 2p. Here's the diagram for the problem: As you can see, the length x is equal to the height of the triangle AEB. I know that if a triangle has equal sides of length ##a## and a base of length ##b##, the...
  10. cwill53

    Mechanics Question- Massive Rope in a Pulley System

    I understand how they might have got to these answers but I'm still kind of shaky on how the mass of the rope plays a role in the tension at point B, and how to mathematically represent the tension at any point along the rope; I know the tension varies because the rope has mass. If I was to...
  11. LuccaP4

    D'Alembert's principle on a pulley system

    This is the problem's picture: My problem is that what I got for one acceleration (m3's) via Newton's equations is not the same as via D'Alembert's principle (I've checked on my PC if they are the same expression). I can't find the mistake. Any suggestion is welcome. I attach pictures of what...
  12. new90

    Virtual work in a pulley system

    If 1kg make a displacement of 1unit upward then A make a 1/2unit down because 1/sin 30.after that i have no idea what do I will really need help. Thanks!
  13. brotherbobby

    Pulling with and without a pulley

    Let me draw a free body diagram for the man. I assume that for both cases (a) and (b), the man pulls the block up with uniform velocity. (1) In case (a), realising that the man is in equlibrium (##\Sigma F = 0##) the normal reaction on the man ##N_a = w_M + T## is given by ##N_a = (50+25)\times...
  14. nish95

    About the constraint equations of a pulley

    See the solved example as shown in the image. I don't understand how can we write S(A)=2S(B) since integrating V(A)=2V(B) will give us an extra unknown constant and the work done by friction will depend on it. I found the relation 2S(B) + S(A) = const. (somebody confirm if this is right?) so...
  15. Rolacycle

    Mechanical advantage of a moving pulley vs an anchored pulley

    This is deer feeder pulley system I plan to make unless there is more efficient way to use the same 6 pulleys and pull load centered between the two poles
  16. jschim

    Oscillating Spring in a Frictionless pulley system

    1. Draw Free body Diagram for each weight. 2. Solve for Tension in Rope. 3. Find Spring Constant. 4. Find omega (w, or angular velocity)
  17. H

    How to change pulley direction?

    Hello Guys, Maybe someone can be at my assistance in this one. I have a similar airer as on the attached picture and i would like to change a set up of pulleys and possibly to add some more of them, in a way that I do not want to pull it down by the side wall anymore. Instead, I would prefer...
  18. A

    Energy conservation for objects hanging from a pulley

    I have some conceptual questions about this task. In order to get the correct result (I checked the textbook answer) in part (a) I had to assume that the speed for each block is the same at all instants. And that if one block moves down x meters, the other one will move up that same amount of...
  19. jisbon

    Acceleration of masses in a pulley system

    So I figured out the equation, but it is probably wrong because the answer doesn't tally. Since the string is inextensible, I can assume that tension is the same for both sides, and acceleration for both masses is the same too So: I can say that the acceleration of 2kg block =acceleration of 7kg...
  20. B

    Length of a string over a 2 pulley system

    Hello all, I am working on a lab report for physics, and am a bit stuck on one aspect. The basic layout of the pulley system is attached. (This is a diagram I made, so if there are any inaccuracies in this one either, I am happy to fix it. So, I mostly understand the lab. My TA said, though...
  21. J

    Inclined plane pulley problem -- lab report help please

    a=m2g-m1gsinø-m1gcosøu/m1+m2
  22. minadd

    Find all forces & the coeff. static friction of a pulley at equilibrium

    Given: (block a) m = .500kg (block b) m = .200kg that's all... Fg (block a) = (.5)(9.81) = 4.905N = Fn Fg (block b) = (.2)(9.81) = 1.962N i think acceleration might go like... a = (1.962)/(.5 + .2) = 2.8m/s^2 but isn't it supposed to be at equilibrium? So 0m/s^2. How am I supposed to find...
  23. kepherax

    Using Forces and Torques to solve a pulley problem

    I am able to solve this easily using energy conservation, but I'm curious how one would go about solving this using forces and torques?
  24. nuclearfireball_42

    Help with a pulley problem with 3 masses

    The figure : What I understand from the figure : T1=m1a1 T2=m2a2 T3-m3g=m3(-a3) - The three masses given all have different mass so each of them has different acceleration - How do one substitute to obtain the answer for a3? - I've tried to substitute to find the value of a3, but it seems...
  25. Kermit_the_Phrog

    Acceleration of a mass lowered by a motor (Help with Non-Ideal Pulley)

    Summary: Non - ideal pulley question, should be easy but has got me good Hey guys, looking for some help on this pulley question. It involves torque, and works with Newton's 2nd law in conjunction with a non-ideal pulley. Text of question: " When the motor in the figure below lowers the m =...
  26. Majd64

    Finding the acceleration of a pulley system including an inclined plane

    This question showed up on my grade 12 physics test. The problem I have with this question is that I did not know the direction that the system would accelerate in, so I just solved as though the mass on the inclined plane would accelerate the system. I expected that if it would accelerate the...
  27. S

    Conservation of energy: a mass and pulley system

    The solution is an application of the law of conservation of energy. Start with equation (1). The masses are in equilibrium and are not accelerating. This implies that ΔK = 0, because the kinetic energy will not change without acceleration. Thus, we are left to find equation (2) in terms of θ...
  28. E

    Analyzing Tensions in a Pulley System: Understanding Mechanical Advantage

    I asume the upper right pulley wire loads will be split in two equally. Therefore, the sum of the loads above pulley equal T1+T2?. To me it appears as if the setup is almost like a 2 to 1 ratio. However, the wires on the left side which are anchored, split the load of the other half of the 2 to...
  29. Like Tony Stark

    Pulley system with relative motion

    Well, first I tried to understand the relation between the velocities and accelerations of both bodies and I got that the velocity of ##B## is half the velocity of ##A##. This is because a change in length of the cord "that touches ##A##" must be equal to the change in length of the two cords...
  30. MPavsic

    Normal acceleration of the Belt on the Pulley

    I have a series of pulleys where the belt is running around them in a way to describe a sine curve. The pulleys are stationary and the belt is running from left to right. For every particle of the belt I can use standard formula to calculate their normal acceleration, when in contact with the...
  31. Gundyam

    Chain Hangs Over a Pulley and Starts Moving

    Homework Statement: A chain hangs over a pulley. Part of it rests on a table, and another part rests on the floor. When released, the chain begins to move and soon reaches a certain constant speed v. Can we find the height h of the table? I think this question need some tricks. I've tried some...
  32. E

    Mechanical advantage of a pulley system

    I don't know how the bottom two pulleys affect the top one. From what I know, the three ropes should have the same tension, the force of the body, divided between them. So if we take top one, it should have that tension on both sides, but also should support the other two pulleys below it. That...
  33. UnPetitGarcon

    The acceleration of a massless pulley in a double Atwood machine

    So there is a textbook physics question in which it asks us to calculate the acceleration of pulley B(which is massless). This exact question was posted and asked previously in this thread. However, it didn't discuss my doubt. To be exact, the question I have troubles with is (b)...
  34. R

    Three masses, a string and pulley and a table -- solve for the acceleration

    Let T be the tension in the string, a be the acceleration of mass 2m, 2a be the acceleration of mass m T = (m) (2a) ---eq(1) The mass 3m will come down with acceleration a’ = (a+2a)/2 = 3a/2 3mg - 2T = 3m . 3a/2 from equation 1 3mg - 2(2ma) = 3m . 3a/2 thus a = 6/17g thus acceleration of 3m...
  35. M

    Pulley Diameter knowing only force and motor specifications

    Hello, How to determine the pulley diameters? The only know factors are listed below. The smaller pulley is attached to a motor that drives the belt drive system. The bigger pulley is driven and has a lifting force of 45N. Known factors: Motor: Pololu 70:1 37Dx54L mm 12V...
  36. KatrineRav

    Acceleration in a pulley system

    SOLUTION ATTEMPT Newtons 2nd law states that F=ma (eq. 1). When a force is applied to a mass m it results in an acceleration a=F/m (eq. 2). If a vertical force is applied to one of the objects in this system, acceleration of both objects will occur. Assuming the length of the rope is constant...
  37. R

    Pulley on Incline: Finding Forces & Tension

    a) I figured this part out. Because A is at rest that means the acceleration is 0 b&c) I am completely lost how to go about this. I drew a free body diagram for A and I was able to determine 4 forces acting on it. 1: The Gravitational force on A (GA). Using the angle (θ), and the incline as my...
  38. C

    Tension on a massless pulley homework.

    please explain
  39. H

    Luffing Jib Load, With and Without Sheave Pulley

    Now I am working with a DIY Luffing Jib Crane. Mys subcon said that: Tension of red rope for hanging a blue box load at the tip of the boom i(A) s as the same as hanging it with pulley and tied to the motor/ground_B (System in a Static Load Condition).. Blue Rope and Pulley weights are...
  40. solarcat

    How Does Net Torque Affect Pulley Acceleration in an Atwood Machine?

    A net torque is required to make the pull rotate, so this can only occur if the tension forces differ. I know mass 1 will accelerate upwards and mass 2 will accelerate downwards, so T1>mAg and T2<mBg. But I don't know where to go from there.
  41. KatrineRav

    Explain friction in a pulley system

    Hi! I'm working in a new area and I'm looking for inputs/suggestions for relevant factors to look into and possible ressource where I can read about this :) I did some tests in a pulley similar to the one below. I had a fixed weight at M2. I started with M1=M2 but added weights to M1 until...
  42. Callista

    What if check: Am I calculating tension wrong?

    Homework Statement Two objects are connected by a string that passes over a frictionless pulley, where m1<m2 and a1 and a2 are the magnitudes of the respective accelerations. Which mathematical statement is true regarding the magnitude of the acceleration a2 of the mass m2? (a) a2<g (b) a2>g...
  43. J

    Describe the position of a pulley attached to a sling

    Hi, I am studying the behaviour of a pulley that is attached to a sling. The situation looks like this: There is a drum that can give or take cable. Then there is a floating pulley with a cable through it. The pulley can move on the circle with a radius the same as the length of the sling...
  44. D

    Pulley system, find the acceleration and tension

    Homework Statement Given the picture: Make the free body diagrams of each body and the pulley. Remember that there are two different strings therefore there are two different tensions.Assuming that the mobile of mass M starts from rest and has a displacement D at a time t, and the bodywith...
  45. I

    Friction problem involving a pulley

    Homework Statement I am posting the snapshot of the problem Homework Equations Moment of Inertia equations The Attempt at a Solution Now, the pulley has the moment of inertia ##I = 1.5MR^2##. This is strange, since the coefficient of ##MR^2## is less than or equal to 1. So, this means that...
  46. PhysicS FAN

    Objects sliding on inclines without friction (connected by a pulley and rope)

    Homework Statement The 2 objects slid on the incline level without friction. The height difference of the objects at t=0 is 8m. At t'=1.5sec the objects are on the same horizontal level. What is the analogy of M/m? (M is the mass of the left object and m the mass of the right object. *Have a...
  47. B

    Pulley question -- Two unequal masses hanging by a string

    Homework Statement Homework Equations F=ma The Attempt at a Solution Okay, so this is probably a really dumb question, but I'm stuck for some reason on it. I drew free body diagrams for each block. For B, there's a small downward arrow for gravity, and a large arrow for tension. For A...
  48. S

    Motion of masses connected by a string over a pulley

    Homework Statement Two particles A and B of masses m and 2m are attached to the ends of light inextensible string which passes over smooth fixed pulley. The particles are released from rest and when particle B has moved h meters, it hits the ground and does not rebound. (i) Find the speed of...
  49. A

    I Alternative approach to analyzing a massless string

    Consider a massless string which can rotate about a fixed pulley (first picture). The coefficient of static friction is μ. Assuming that the motion is impending, the goal is to find the equation that describes the variation in tension of the string. ( T2/T1 = eμΦ where Φ is the subtended angle.)...
  50. K

    (Mechanics) Pulley System Question

    Homework Statement Derive an expression for the angle alpha and determine the initial horizontal and vertical forces exerted at the point of attachment of the bell rope to the plank. The system is in static equilibrium Both ropes are light ie negligible mass. The point of attachment has been...
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