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Pulleys

PLEASE NOTE: Some of the videos in this section are silent to allow the viewer to make their own observations about what is happening and respond to the questions posted below.
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This video has no sound
1. Does this pulley arrangement give you a mechanical advantage?
2. If it does not give you a mechanical advantage why would you use it?
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This video has no sound
1. Why were two fixed pulleys used at the top of the crane?
2. How far does the gondola on the right move compared to the one on the left?
3. Which gondola has the mechanical advantage?
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This video has no sound
1. Why were two pulleys used on top of the gondola on the right?
2. How far does the gondola on the left move compared to the one on the right?
3. Which gondola has the mechanical advantage?
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Simple machinesSee video transcript
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Pulley Motorized 1See video transcript
1. How would you fix load tilt in the first part of the video?
2. What is your mechanical advantage in the pulley system shown at the end of the video?  (Hint: look at the movable pulley in the center of the load)

Want to join the conversation?

  • aqualine seedling style avatar for user Summer A.
    Whoo, first question ok! So looking at the figure in in the Simple Machines video specifically, I'm intuitively confused about how we "lost" 50N of force/ only have to exert 50N to pull a 100N block? What happened to the other 50N? Who's pulling that part? Also, if we assume that both pulleys are massless, what is the force on the "bar" holding the fixed pulley, and the force (tension) and direction of force on string 1 and 2?
    (3 votes)
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  • duskpin ultimate style avatar for user Ainsley M
    what's the point of a fixed pulley if there's no mechanical advantage?
    (2 votes)
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  • marcimus pink style avatar for user mreid
    This is really col but i don't know if I have all the stuff to make this,isn't there an easier way to make it.
    (4 votes)
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    • starky tree style avatar for user Vedanjali
      why not take a tube like object (a desk lamps adjustable neck) that is suspended in mid air. take a string and tie it round a eraser and then put the string over the top. that way when you pull the non eraser end the eraser will rise up. just like a pulley! YAY!
      (4 votes)
  • starky ultimate style avatar for user Andreas.Stasi99
    Please review, and correct my thoughts:

    Video 1:
    Q1. no mechanical advantage.
    Q2. Can use this, so that instead of lifting something above your head (against gravity), you can push something else down and work with gravity.

    Video 2:
    Q1. No idea, but I can see the effects i.e. A heavy gondola on the right can easily be raised. A force downward on the left, causes a much larger upward force on the right.
    Q2. The right gondola moves approximately half the distance of the one on the left.
    Q3. Since the right gondola moves half the distance, it implies that it also requires double the force. Therefore, a force on the left applies about double that force to the right, indicating a mechanical advantage to the right gondola.

    Video 3:
    Q1. So that the left can apply a large force over a small distance causing the right to travel a large distance with a minimal force applied.
    Q2. The gondola on the left travels much less distance, approximately 1/4 the distance travelled by the right gondola.
    Q3. The gondola on the left requires more force, therefore, it has the mechanical advantage.

    Motorized Pulley Video:
    Q1. Didn't quite understand what was done to even it out.. I had my own idea, but it wasn't the technique used. My idea: Add an identical second motor and wheels on the right side, which would cause the weight to tilt to the right. Thus, the same force is applied on either side.
    Q2. I need to understand question 1 first! - But thoughts: The pulley wheel on the right requires the most amount of force, therefore, it has the mechanical advantage?
    (3 votes)
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  • leaf red style avatar for user Aralqua
    At , why does he bother to count the number of movable pulleys if all you need to know is the number of ropes? I know you need to know which are the movable pulleys, but why count them?
    (3 votes)
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  • piceratops sapling style avatar for user threet_myka
    why did you move the bateries when you fixed the floss
    (2 votes)
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  • starky sapling style avatar for user Sahana Rukmangathan
    what is better for lifting heavy objects a pulley or a lever
    (1 vote)
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    • duskpin ultimate style avatar for user Chermosil
      Pulley pros:
      1. Easy to transport (if you attatch a pulley system to a crane, for example)
      2. Able to lift the object much higher

      Cons:
      1. Non-efficient for small tasks
      2. Time-consuming to make

      Lever pros:
      1. Easy to make.
      2. Object easily slides off the lever to destination

      Cons:
      1. It's almost impossible to push a lever and an object at the same time so it's not really great for transport.
      2. Cannot lift objects straight (it will tilt to one side) so if you were carrying, say, a big basket of some sort with items inside, the items inside the basket could fall out due to the tilting.
      3. Not great for lifting things off into the sky.

      So to answer your question, it depends on what the situation is. Hope this helps!
      (2 votes)
  • leafers sapling style avatar for user Ashmita Pilania
    How is the mechanical advantage equal to the number of strings?
    (0 votes)
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    • male robot hal style avatar for user Charles LaCour
      The tension in the string is the same throughout the pulley system. If you look at the the tension on the strings that are doing the lifting you will see that if there is 1 string there is 1 times the tension lifting but if you have 2 string you have twice the tension lifting so the lifting force it is directly proportional string tension times the number of strings.
      (3 votes)
  • blobby green style avatar for user michael.relleum
    Would the MA on the last motorized pulley be 3? Because it has 6 ropes attached to moveable pulleys, but the motor is pulling twice now so MA halves?
    (1 vote)
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  • primosaur ultimate style avatar for user Alden Chen
    So the more strings on one side of the pulley = less distance?
    Does the strings even the distance out?
    (1 vote)
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