What is Pulley: Definition and 1000 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. runningphysics

    Two masses connected by a rope on a pulley on a ramp

    I have no clue how to do the problem. I created a free body diagram for each block. I assume that it is simpler than I am making it out to be.
  2. rudransh verma

    Exploring the Advantage of Using Pulleys in Two Block Problems

    ##(T-m1g)-(T-m2g)=(m1+m2)a## But I think this is wrong eqn.
  3. rudransh verma

    B Atwood machine -- Question about the pulley and weights

    I want to ask in this machine when there are two masses hanging down then the tension T is directed upwards along the rope. Is it the force applied by the rope on the mass? Is it the force applied by the pulley? When the anyone mass of the machine moves downwards is it because the force of...
  4. rudransh verma

    Two bodies hanging from pulley

    ##(T- m1g)-(T-m2g)= ( m)a##. I don’t know what m?
  5. erensatik

    Tension in a pulley system pulled at an angle

    This problem just came to my mind when thinking on another problem. Does the tension is just 2T as it is if the angle "a" is 90 degrees? It seems not to me. In a "normal"( I don't really know what is the right word for that) situation, the tension is would be 2T at the line in the middle of two...
  6. P

    I Preloading Pulleys: Understanding the Effects of Tension on Angular Velocity

    I am making a system Where I am pulling on opposite ends of a pulley with Tensions T1 and T2. Is this equivalent to preloading the pulley with tension T2? If I preload the pulley with T2 on a separate rope, how will the angular velocity change when I apply T1? I've drawn a quick diagram
  7. S

    Using the sin function for a problem with a frictionless pulley and an incline

    To find the tension in the rope connecting 6.0 kg block and 4.0 kg block we do 6.0 kg = m1, 4.0 kg = m2, 9.0 kg = M (m_2 + m_1)a - Ma = Mg - m_2 gsin\theta - m_1 gsin\theta Why do we use sin in these equations and not cos?
  8. T

    Angular Velocity: Pulley and belt system

    So far I have: The velocity of the belt will be the same for pully A and D, so we can calculate the angular velocity of pulley D: ## V_A = V_B ## ## \omega_A r_A = \omega_D r_D ## ## ((20*3)+40)(0.075) = \omega_D (0.025) ## ## \omega_D = 300 Rad/s ## My next step was to determine the angular...
  9. burian

    B Relating displacements in a pulley system

    > The set up: At left end, the rope is pulled down with a distance $dx_1$ by a force of constant magnitude $F$, the mass of $M$ is wrapping around by rope on the right and moves up by a distance $dx_2$ due to this. Problem: Find relate the two displacements. I thought of applying energy...
  10. dabbih123

    Find the unknown mass on a inclined rope pulley system.

    First I calculated the forces that were working against mass B. m(A)g sin 30 + μm(A)g cos 30 = 12.86 N The force working with mass B is m(B)g = 9.8m(B) I thought I could solve for B using F=ma where 12.86 N = (2kg+m(B))*(0.58), but of course, 12.86 N is just the force required to make the...
  11. vibha_ganji

    Halliday, Resnick & Krane Chapter 5: Force on Pulley

    As the force on a pulley is equal to twice the tension, I just have to find the tension to solve part A. To do so, I first wrote the equations for both m1 and m2. m1 * a = T - m1g m2 * a = T + N - m2g The tension must have the same values for both equations so I added both equations to find...
  12. S

    Finding the period of pulley system

    This is not homework. I found this question when browsing and there is also solution but I do not understand it. This is part of the solution: My questions: 1) From equation (i): ΔT = m.a, I think ΔT refers to W - T (weight of block - tension of string). I got this from free body diagram and...
  13. T

    Question on problem 2.16 (a) of the Feynman Lectures (two-mass pulley)

    My attempt was to calculate the acceleration of M2 as the acceleration of M2 if it were the only mass in the system, minus the component of M1's acceleration along the slope. And then I would divide the whole thing by 2 to get the acceleration for just one of the two masses@ a = 1/2 ( g -...
  14. lucaszito

    Pulley system for cardboard pulp shredder/mixer

    Hi everybody, first message on this forum ! I am building a machine for a friend who works with cardboard pulp, he is also a performance artist and would like a machine where 2 or 3 performers can activate the machine by hand with pulleys and wheels, and shred the pieces of cardboard that are...
  15. F

    Pulley system -- Calculate the mass that balances this pulley system

    I've been stuck at this pulley system for a while. I've calculated the force of which A pulls => FA = sin25*50*9.82 = 208.5 N But I get stuck on the free body diagram. Can someone help and explain the freebody diagram
  16. B

    How to solve mass-spring system when affected by torque in a pulley?

  17. V

    Ideal Vs Real Mass Pulley system

    Below is an ideal mass pulley system that we encounter in many problems under Newton's Second Law of Motion questions. Its supposed to be massless and frictionless i.e. string slips over the pulley and pulley does not rotate. In a real system, the pulley is assumed to be massless, whereas in...
  18. R

    How can I calculate the load on each line in a pulley system?

    Hello, I'm working with a pully system and can't find the answer for this question on Google. I'm wondering how to calculate the load on the rope in order to determine what grade rope I should use. For example let's say I'm picking up a 100 lb box using a 4 to 1 system. Not accounting for...
  19. V

    What is the energy conservation principle in a two masses and pulley problem?

    i) I first analyzed the forces as soon as the 14 Kg is released. The aim of this step is to calculate the work done by the net force acting on the 14 kg mass to determine the change in kinetic energy. T-14g=-14a T-8g=8a T=99.7 N a=6g/22 m/s^2 Since the net force is constant and does not vary...
  20. P

    If I pull a pulley, what is the tension in the string around it?

    I assumed that each of the masses attached to the string would be pulled with a force F, instead of F/2, which appears to be the correct value. Why is it F/2? I suspect the fact that the pulley is "weightless" has something to do with the F/2 value. What is it? Thank you.
  21. K

    Finding the torque required for telescopic cable mechanism

    Summary:: I am designing a linear telescopic system that gets elevated with a step motor, but in order to find the compatible motor, I need to work out the torque that is required for the elevation. I have uploaded my CAD model to this thread with how cables are connected. Could someone please...
  22. hquang001

    Pulley and Blocks: Is My Answer Correct?

    1 Block m2: m2g - 2T = m2a2 (1) Block m1: ∑F= ma T= m1a1 = m1.2a2 (2) Cancel T in (1) and (2) I have : m2g = a2 (4m1 + m2) => a2 = m2g / (4m1 + m2) => a1 = 2m2g / (4m1 + m2) Is my answer correct ? Thank you
  23. S

    Acceleration of objects connected by pulley on rough inclined plane

    Summary:: Please see the picture below Let say: ##W_1## is weight of ##m_1## ##W_2## is weight of ##m_2## ##f_1## is friction on ##m_1## ##f_2## is friction on ##m_2## I want to find the acceleration of the system. Since I don't know in which direction they will move, I just assume ##m_1##...
  24. A

    Friction between pulley and rope

    I have a question about friction between pulley and rope? Does anyone know how to calculate friction between pulley and rope I enclosed an example picture Thank you!
  25. I

    Find the load saved by a pulley system

    There are 3 different strings in this system. The one pulling P, the one pulling F and the one pulling a pulley. Since the questions says they're ferried across before hitting mast or deck, I'm assuming that they are not stationary. g is gravitational acceleration. P will move twice as fast...
  26. mustafamistik

    Newton's Second Law of Motion -- Three masses, an inclined plane and a pulley

    I did part a and part b but stuck in part c. Could you help me? (Part a and b attached.)
  27. mattlfang

    Find the velocity and acceleration of a pulley in a mass-spring system

    This looks like a classical setup but I can't find a solution. We can calculate the energy of the system by looking at the work done by the gravity and the spring. But how do we divide the energy between the kinetic energy of the pulley and the rotation of the pulley?
  28. sahilmm15

    A classic string and pulley problem

    I tried hard but was not able to make progress. Problem no 33.
  29. T

    Moment of Inertia with pulley and two masses on a string (iWTSE.org)

    Note: the working (taken from iWTSE website) refers to inertia as the symbol ‘J’ (in-case there was any confusion).I found equations of motion for mass m and 2m which were ‘T1 = ma + mg’ and ‘T2 = 2mg – 2ma’, respectively. I know they are connected particles with the same acceleration ‘a’.I have...
  30. N

    Statics Problem -- A bucket suspended between two walls by a rope and pulley

    I approached this question with a free body diagram. my Verticle length of BA is y-2 AC= 15-AB Horizontal length of AC= a; Horizontal length of BA=10-a I have too many unknowns in this problem and I don't know any directions(angle). I know that I should start at the weight and try to resolve the...
  31. goodOrBad

    Two blocks connected by a rope over a pulley

  32. goodOrBad

    Feedback on the concepts surrounding pulley, ropes, friction

  33. pkreilley

    Two Masses, a Pulley, and an Inclined Plane

    I solved for T on m1 and arrived at 6.72. I plugged that value into the ΣFx equation as shown above (pardon my handwriting) and got a mass of 0.88 kg. The online program indicated that I needed to check my expression for tension, noting that the two tensions are heading in opposite directions...
  34. E

    Pulley and Two Masses -- Newton's Law of Motion

    From this question, I do not understand why there are three forces exerted at Point C (2 of it being the tension by weight A and the other is the tension by weight B) I understand that there is tension by the two weights but why is there 2 forces exerted by weight A at point C? From the...
  35. N

    Why Is My Calculation Result for Acceleration Incorrect?

    Fsp = 90 x 0.12 = 10.8 Ffriction = Magcos(titre) x 0.30 I got the answer 2.09ms2 when the correct answer is 1.11ms2. What am i doing wrong here?
  36. M

    Forces: Pulley and Slope Constraining the Motion of two Masses

  37. Hamiltonian

    Does the tension in a string act on the body to which the pulley is attached?

    The normal reaction from the ground and from block m, the force of gravity are the forces I feel should act on the wedge but since the wedge is a perfectly rigid body and the pulley(which is massless) is attached to it so will tension also act on the wedge as well?
  38. B

    Choosing proper coordinates in a complex 2 pulley system

    FBD Block 1 FBD Block 2 FBD Pulley B I'm mainly concerned with the coordinate system direction in this problem, but just to show my attempt, here are the equations I got from the system. ##-T_A + m_1g = m_1a_1## ##T_B - m_2g = m_2a_2## ##T_A - 2T_B = 0## Using the fact that the lengths...
  39. burian

    Trajectory of a mass element in a string overhanging a pulley

    Hello everyone, this is a thought experiment I made, it involves two ropes being pulled of a pulley similar to an atwood machine, and a block attached to the two pulleys at the other end. The ropes are being pulled at a constant velocity $ U$ from the end away from the block and the block rises...
  40. aspodkfpo

    Exploring Force Pulleys: The Surprising Truth Behind Non-Net Forces on Objects

    If a free body diagram is constructed for 1kg, one might be inclined to draw an arrow downwards with only the weight of 10N. However, the downward, non-net, force on 1 kg is (1+5) x 9.8. Why is this the case? It seems very counterintuitive.
  41. Adesh

    (I.E. Irodov problem 1.72) Dynamics problem involving a pulley

    . First thing that I notice is that the other part of string (to which body 2 is connected) is fixed. Therefore, I concluded that the body 2 is stationary with respect to the pulley 2 (let's agree that pulley to which body 1 is connected is pulley 1 and in same way pulley 2 is defined)...
  42. T

    Conservation of energy problem: Two masses, a pulley and an incline

    If M moves ##x## along the plane, her height variation in ##x \cos(\alpha)##, and, but I don't know how to find the variation of the height of ##m##
  43. andrewkirk

    1 pulley with mass, 1 mass on the cord, 1 external force, no gravity

    I remember, a few weeks ago, when looking for homework problems I could help with, seeing one as described in the title. I couldn't think of an easy solution and was busy at the time so i made a mental note to think about it later. I finally got around to doing that yesterday, and brushed up on...
  44. J

    Air Cylinder connected to a Lever that drives a Pulley for Applying Belt Tension

    Hi, I am looking for some guidance on how to approach this calculation. I have an air cylinder operating a lever assembly that then applies pressure to a pulley of which a belt is wrapped around. I need the belt to have about 4500 lbs of tension. How do I work backwards to figure the required...
  45. 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...
  46. 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.
  47. 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.
  48. 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...
  49. 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
  50. 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)...
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