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

    Trouble understanding Newton's Third Law in Pulleys

    Hi everyone. I found this image online that made me question a couple of things that might be a bit humiliating to ask: I always thought that tension is simply a pulling force, meaning that the mass is suspended because the tension force pulling the mass is equal to the weight force of the...
  2. E

    Newton's laws -- Blocks and pulleys problem with friction....

    Homework Statement The coefficient of friction between A and the table is μA. The coefficient of friction between A and B is μB. A, B, C and D all move with an acceleration of 2m/s^2 (A and B move to the left). Find the force that the friction between the bodies apply on B. Find the tension of...
  3. Francis Hannah

    The mass of an object with pulleys

    A block is lifted by the pulley. Where θ=37.9 degrees and F=112N, find the mass of the block in kg. I know that tension T1=T2=T3. So, T3=112⋅cos(7.1)=111.14 Hence, T1 and T2 are equal to 111.14 as well. Thus, mg=(2)⋅(111.14)⋅cos(37.9)=175.40? And thus the mass is < 175.40/9.81 ⇒ mass <...
  4. D

    Force problem with three masses and two pulleys

    Homework Statement For the apparatus in the figure, what is the minimum value of the coefficient of static friction between the block (m3) and the table that would keep the system at rest if m1 = 0.10 kg, m2 = 0.20 kg, and m3 = 0.30 kg? (Assume ideal conditions for the string and pulleys.)...
  5. J

    Statics Problem involving blocks, rope, pulleys and springs....

    Homework Statement The angle at the bottom is 25 degrees Homework Equations Springs Parallel; keq = k1 +k2 Sum Forces = f1 + f2 x = f1/k1 = f2/k2 Springs Series; 1/keq = 1/k1 + 1/k2 Sum x = x1 +x2 F = k1x1 =k2x2The Attempt at a Solution Basically I'm having trouble finding the spring...
  6. deuce123

    Pulleys with friction , FORCES

    Homework Statement A cord connected at one end to a block which can slide on an inclined plane has its other end wrapped around a cylinder resting in a depression at the top of the plane as shown in (Figure 1) . Determine the speed of the block after it has traveled 1.60 malong the plane...
  7. N

    Pulleys, Pulleys, and More Pulleys

    Ok so I will attach an image of two pulley systems. The one on the right is straight forward. Both forces are vertical so the force pulling down on the pulley is easy to figure out. The one on the left makes me a bit more confused. For the one on the left I was wondering if the combined vertical...
  8. N

    Pulley Carrying Capacity: Can It Handle 150 lbs?

    Ok, so I just started researching about pulleys. Fascinating simple machines. I had a question about their carrying capacity (don't know if that's the technical word for it but work with me here). Let's say we have a two pulley system. One fixed on the ceiling, one moveable on attached to the...
  9. person123

    Exploring Pulley System Equilibrium: Solving for y when x Changes

    I was working on a pulley system as shown here: The mass on the right and left side is equivalent, and I am solving for when the system is in static equilibrium. Theta is the angle between the rope on either side of one of the pulleys. H and y are both measured from the original position of...
  10. Bunny-chan

    Conservation of the string length in pulleys

    Homework Statement This is a common massless string and pulleys problem. I'd just like to understand why, according to the solution, l_2 + 2l_1 = constant. It doesn't seem to me that two times the l_1 length is equivalent to l_2. Can somebody explain? Homework EquationsThe Attempt at a Solution
  11. Alok

    How pulley diameter affects forces?

    Whether the diameter/radius of pulley affects the force required in lifting a weight?
  12. B

    Relations between torque for system of pulleys

    Homework Statement In an attempt to find a transfer function of the system, I need to come up with equations that I can use to solve for unknowns. See the attached image to see the diagram of the pulley system. J is the moment of inertia, r is the radius. The smaller radius on pulley 2 is r1...
  13. anony123

    Why does adding more pulleys increase the force on a block?

    Hello, First of all, I'm new to this forum and to not know whether this thread is in the right place or not. If not, feel free to replace it. I'm in my first year of university, studying industrial engineering. On a test I got the following image: The red square is a block with a specific...
  14. vinamas

    Two pulleys and two masses on a slope

    1. The problem statement, all variables Use this photo http://m.imgur.com/a/lQd9q Two masses are connected to two pulleys via ropes.The mass of the hung mass is 16kg and the mass of the object on the slope is 8kg the slope has an angle of 37 degrees. Pulleys 1 has a mas of 6 kg and Pulley 2...
  15. U

    Constant string length question with pulleys

    Homework Statement Given Ma = Mb =Mc and muk between c and the surface is 0.30 Homework Equations (rope length) = constant Maaa = Mag - T Mbab = Mbg - 2T Mcac = T - (mu)Mcg The Attempt at a Solution The equations I came up on my own and the answer key did as well. The problem is I also need...
  16. U

    Dynamics -- Velocity of a Block in a system of Pulleys

    Hey guys, I have been a long time lurker here but this problem has eluded me for a few hours now and my frustration at not being able to figure out what it is I am missing prompted me to finally pull the trigger on making an account here. I hope the way I wrote everything out is clear to...
  17. Al_Pa_Cone

    Calculating Power/Torque transmitted between 2 pulleys

    Homework Statement Q1. A pulley 150 mm diameter is driven directly by an electric motor at 250 revs min–1. A V-belt is used to transmit power from this pulley to a second pulley 400 mm diameter against a load of 200 Nm. The distance between the centre of the pulleys is 600 mm, the...
  18. U

    Relative velocity problem with pulleys

    Homework Statement Homework Equations Vb/a = Vb - Va The Attempt at a Solution I got as far as realizing that the velocity of B depends on A so I wrote out: 2(Xa) + (Xb/a)cos15 = constant and took the derivative of that equation to get Vb/a = -16.56. I then got stuck as to how to get Vb...
  19. Valerion

    Two masses, two pulleys and an inclined plane

    Homework Statement A block of mass m1 is at rest on an inclined plane that makes an angle (theta) with the horizontal. The coefficient of static friction between the block and the inclined planed is µs. A massless, inextensible string is attached to one end of the block, passes over a fixed...
  20. Haniah

    Calculating Toolbox Mass in Horizontal Pulley System

    Homework Statement A group of construction workers are building a house and want to lower down an excess bundle of 1400 kg bricks to ground. They tie one end of a rope to the bundle of bricks, loop it through a pulley, and tie the other end of the rope to a toolbox. If the coefficient of...
  21. S

    Help With Pulleys: Answers to Acceleration Questions

    A block of mass m1 is attached to a block of mass m2 by a massless rope (see diagram); the pulleys and surfaces are frictionless. When the blocks are let go, they move. Answer the following three questions using the choices given below. i) Select the correct expression for the relationship...
  22. K

    Masses and combined pulleys

    Homework Statement 1) Which mass accelerates faster than g 2) What's m1's acceleration 3) In which condition m3 will move upwards, if they start from rest Homework Equations Mass-acceleration: F=ma The Attempt at a Solution $$\left\{\begin{array}{l} (1)~a_3=2a_2+2a_1 \\...
  23. K

    What is the Maximum Ratio of m1 to m2 to Keep m1 Stationary in a Pulley System?

    Homework Statement [/B] m1 must stay in place. express m4 with the rest. What must be the maximum ratio ##\frac{m_1}{m_2}## in order m1 will stay in place. Homework Equations Mass-acceleration: F=ma The Attempt at a Solution 2 cases, in the first ##m_1<m_2##, which is drawn above...
  24. K

    What is the acceleration of two masses on pulleys with constant tension?

    Homework Statement All N+2 masses are m. what is the acceleration of the 2 masses at the ends. Homework Equations The rope on a weightless pulley has constant tension. The Attempt at a Solution The situation is the same as: $$\left\{\begin{array}{l} Nmg-2T=Nma \\ T-mg=ma...
  25. Mr Davis 97

    Two masses and two pulleys problem

    Homework Statement Masses M1 and M2 are connected to a system of strings and pulleys as shown. The strings are massless and inextensible, and the pulleys are massless and frictionless. Find the acceleration of M1. Homework Equations Newton's 2nd Law of motion The Attempt at a Solution So...
  26. S

    Calculating Torque for Inclined Pulley System with Steel Rails and Heavy Load

    This was a pulley question that was presented to me today at work. They are using two pulleys, one is driven by a gearbox, the other is sort of an idler, between the two pulleys there is a total of 6 wraps. They are trying to pull a 8000lb cart up and down a straight incline of 5 degrees over...
  27. S

    Can Conservation of Energy Explain Pulley and Inclined Plane Mechanics?

    Homework Statement Homework Equations Conservation of Energy / Virtual Work $$\sum_i m_i g h_i = 0$$ The Attempt at a Solution Moving the pulley I labeled A down by ##\delta y## moves ##w## down by ##\delta y##, and moves ##W## up by ##\frac{1}{2} sin\theta##. So by conservation of energy...
  28. C

    Understanding the Motion of Double Pulleys: Exploring Acceleration and Forces

    Homework Statement A mass m1 is hung on a pulley with another pulley on th eother side with two masses;m2 and m3.Find the accelerations of the masses Homework Equations F=M.a a1=-(a2+a3)/2 The Attempt at a Solution So in my book ,the solution provided was 2T-m1g=m1a1 T-m2g=m2a2 and T-m3g...
  29. D

    Coefficient of Friction of Fixed Atwood Pulley

    Homework Statement Hi, I was wondering how you would isolate for and calculate the coefficient of friction in an Atwood pulley, with one fixed pulley, with two masses hanging off of it on either side. There is no table or surface that the masses are touching or resting on, they are both...
  30. S

    Pulleys & Masses: Instantaneous Acceleration

    Homework Statement Consider now the case where the string of length l has mass per length λ ̸= 0. Show that the instantaneous acceleration of m2 is given by a2 = (m1 −m2)+2x0λg/(M + m1 + m2) where M = λ l is the total mass of the string and find the tension in both ends of the string. (please...
  31. A

    Newton's laws of motion -- masses on pulleys....

    Homework Statement Wasnt able to upload file, therefore an external link https://drive.google.com/file/d/0B0FIIKckKOcKWFcxcmtJRVRXZTA/view?usp=drivesdk A force F= mg is applied on C, all pullies are frictionless and we need to find the reading of the spring balance, basically the tension...
  32. wirefree

    Is My Approach to Calculating the Length of a Rotating Compound Pulley Correct?

    I am appreciative of the opportunity afforded by this forum to submit a query. Problem: See NOTE: The reference to weight "D" in the second line is incorrect. My Attempt: Step 1: Since this is a constant acceleration situation, I calculated the angular acceleration = 3 cm * -4 cm/s/s Step...
  33. T

    Pulleys with a mass and radius

    Homework Statement Block A has a mass of 3 kg, and block B has a mass of 8 kg. Determine the speed of block A if it moves upwards 2 meters, starting from rest. I can solve the problem pretty easily if the mass and radius of each of the pulleys is neglected. However, if they are not neglected...
  34. H

    Pulleys, displacement by vertical height

    Homework Statement (see attached diagram) Homework Equations (see attached diagram) The Attempt at a Solution I drew a diagram.What I know. Left part of rope is fixed to ceiling so extra rope comes 'from the right' i.e. 'falls down' as pulley is pulled. I also know that rope is conserved.
  35. R

    How to investigate pulleys and belt

    Hi. Me and my team are re-building a human powered aircraft's transmission system, and are currently designing the part of the pulley and belt. We've bought the belt and pulley quite some time ago from different shops, thus, we now have to re-investigate whether the pulley and the belt match...
  36. T

    Solving for Acceleration in a Complex Pulley System

    1. Homework Statement What is the acceleration of m1? There is no friction so the pulleys don't rotate. The top rope is connected to the ceiling. Homework Equations See photo. I think my formula for the acceleration of M2 is only right if m1 = m2 and wrong in all other situations, but I'm not...
  37. putongren

    Question involving 2 pulleys and 2 masses.

    1. Homework Statement If the magnitude of the acceleration of block m1 is a, what is the magnitude of the acceleration of block m2? Homework Equations None. The Attempt at a Solution The answer is 2a. Is it because the top string of the right pulley is adding string, while simultaneously...
  38. U

    Exploring the Effects of Friction and Rotation on Tension in Pulley Systems

    [mentor's note: Spilt from https://www.physicsforums.com/threads/tension-questions.852525] How does friction in a pulley or a rotating pulley change the uniform tension in a rope that was present in an ideal situation? Thanks!
  39. komarxian

    Help with Forces, Pulleys, and Whether People get pulled

    Homework Statement A rope of negligible mass passes over a pulley of negligible mass attached to the ceiling, as shown above. One End of the rope is held by Student A of mass 80 kg, who is at rest on the floor. The opposite end ofthe rope is held by Student B of mass 70 kg, who is suspended at...
  40. komarxian

    Calculating Acceleration and Tension in a Pulley System with Inclined Planes

    Homework Statement Block A has a mass of 75 kg and is initially at rest on a frictionless inclined plane tilted at a 37 ° above the horizon. Block A is attached to a massless rope that is connected to the top of Block B by way of a massless frictionless pulley. Block B also has a mass of 75 kg...
  41. S

    3 pulleys - 2 masses on incline plane

    Homework Statement http://tinypic.com/r/qs9q4o/9 http://tinypic.com/r/qs9q4o/9 Verify that the log will move up the ramp under the given conditions Homework EquationsThe Attempt at a Solution m1 = 220 m2 = 130 mu = 0.4 theta = 25 g = 9.81 N = (m1*g)*cos(theta)1) m2g – T = m2a Forces...
  42. Gbox

    Accel of 2 Masses & 3 Pulleys: F=Ma Solution

    Homework Statement Find the acceleration of the masses Homework Equations ##F=Ma## The Attempt at a Solution We know that the system is moving so for ##M_1## we have ##M_1gsin\theta## on the other hand on ##M_2## we have ##M_1gsin\theta-M_2gsin\theta## How can I conclude that the...
  43. dumbdumNotSmart

    Tension on pulleys with mass

    Homework Statement Hey guys. The other day I was doing some physics questions, studying for the finals, you know the story. Me and my friend came across this physics question where: There is a particle of mass 2kg (m) hanging by a mass-less string that went around a pulley with mass 4kg (M)...
  44. L

    How to Calculate Sag in Terms of Weight, Pulleys, and Distance?

    Homework Statement A pulley to which is attached w1 rides on a wire that is attached to a support at the left and that passes over a pulley on the right to weight w.the horizontal distance between the left support and the pulley is L.Express the sag d at the center in terms of w,w1 and L. The...
  45. J

    Pulleys Jh Homework Statement: Understanding the Concept of Pulleys

    Homework Statement https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfl1/v/t34.0-12/12231095_1486035821701632_2065647312_n.jpg?oh=dd0658f6afcfe91a852c72c3dab01560&oe=564836A2&__gda__=1447576857_f29a19be54068711687d57ac9593225d Homework Equations None The Attempt at a Solution None[/B]
  46. B

    Relative Velocity problem: 2 pulleys riveted together

    Homework Statement As shown in the picture, two pulleys are riveted together with a known velocity. I need to find the velocity of two other points. Homework Equations V_A = VB + <ω> x <BA> V = ωr The Attempt at a Solution I've honestly been trying to figure this one out for over a...
  47. L

    Acceleration and Tension in Multiple Pulleys

    Homework Statement Block "m1" sits on a horizontal frictionless surface. Block "m2" is hanging below the pulleys as shown. All of the pulleys are massless and frictionless. Given [m1, m2]. Determine: a. The tension in each rope. b. The acceleration of each block. Homework Equations Sum(F) =...
  48. moenste

    Find masses of particles on pulleys attached by strings

    Homework Statement A particle A is suspended as shown in the figure by two strings, which pass over smooth pulleys, and are attached to particles B and C. At A, the strings are at right angles to each other, and make equal angles with the horizontal. If the mass of B is 1 kg, what are the...
  49. DanielleG

    Tension and Pulleys theory question

    Homework Statement 17. Give the correct tension, T, in the marked rope for each situation. The rope is held so the system is stationary. All ropes and pulleys are massless and frictionless. A) T = W B) T = W/2 C) T = W/3 D) T = 2W E) T = 3W/2 F) T = 2W/3 G) T = W/7 H) T = W/5...
  50. Thornak

    Force With a Pulley: Theoretical and Experimental

    Homework Statement [/B] This is not a typical homework problem, so I hope I am posting this in the correct place. I am in 12th grade physics and we are dealing with basic kinematics. However, we recently did a set of problems that I did in a way which makes sense and which our textbook (and the...
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