Wednesday, April 11, 2012

Pulleys Everywhere?

Photo by emkladil.

We've been studying simple machines in class, and we've talked about lots of examples of each type. In this post, I'd like us to focus specifically on pulleys:

  1. Sometimes, a pulley simply changes the direction of a force without increasing the force. Therefore, the mechanical advantage (MA) is 1. Other times, pulleys can be used to increase a force (and have mechanical advantage of much greater than 1). How can this be? How can you tell just by looking at the pulley whether or not it will increase the applied force?
  2. Where are pulleys used in practical applications?
  3. Look carefully at the pulley in the photo at the top of the page. How might this pulley be used?



Posted by Brian Bearss at 8:38 AM

14 comments:

  1. MithosApril 12, 2012 at 7:16 PM

    I believe that with more pulleys, the amount of input force needed decreases. And since the formula for Mechanical Advantage is Output force divided by the input force, you will get a much higher Mechanical Advantage.

    Pulleys can be used to lift a crate or other objects by pulling to the left, instead of directly up. This could make the job easier to perform.

    I think the pulley in the photo could be used to change the direction of a force to make a job more simple.

    ReplyDelete
  2. BabeRuth17April 12, 2012 at 9:19 PM

    1. I agree. I think that the more pulleys you have then the less input force is needed. With a higher output force than input force, you will get a higher mechanical advantage.

    2. Pulleys are used to lift objects such as a box. Also a pulley is used to raise a flag on a flag pole. Pulleys are found in vacuums and in agricultural tractors too.

    3. I think the photo shows a pulley that is in a easier direction to pull. It could be used for a clothesline for example :)

    ReplyDelete
    Replies
    1. ilovesportsApril 15, 2012 at 1:11 PM

      Good thinking of pulleys being able to raise a flag pole! It is kind of hard to think of good examples of pulleys being used in everyday life in today's time.

      Delete
  3. Ms.Sunshine95April 14, 2012 at 3:13 PM

    1. Mechanical Advantage is higher if the Output force is higher.

    2. Lift objects, raising flags, cars have them, Elevators are pulleys, washing machines, conveyor belts, and construction work.

    3. To make work/ a job easier and usually quicker.

    ReplyDelete
  4. ilovesportsApril 15, 2012 at 1:09 PM

    1. As our lab in class showed, you can tell that the MA is greater than 1 if there are additional loops making there be more smaller strings pulling on the object.

    2. Some pulleys are used to get water out of a well and to lift heavy objects.

    3. This pulley could be used to slide heavy objects across the ground.

    ReplyDelete
  5. AnonymousApril 15, 2012 at 1:46 PM

    1. I agree with the others that a higher output would increase the MA. Also this would effect the efficiency.
    3. I think this pulley could be used to lift something heavy.
    Iloveweekends

    ReplyDelete
  6. AnonymousApril 15, 2012 at 7:00 PM

    i agree with mithos that more pulleys makes you use less force and that the pulley in the picture may be used to change the direction of a force

    mason smeznik

    ReplyDelete
  7. AnonymousApril 15, 2012 at 8:41 PM

    pulleys can be used anywhere like pulling heavy objects up such as boxes crates and other things. this pulley could be used for a clotheline like baberuth17 said

    mason smeznik

    ReplyDelete
  8. Brian BearssApril 15, 2012 at 8:53 PM

    I think you're all missing something quite obvious about this pulley. Look carefully at that little gear wheel... ... what is it for? What is that rectangular metal object?

    ReplyDelete
  9. iloveXCApril 15, 2012 at 9:52 PM

    2) Pulleys can be used everyday in elevators, and also in the conveyor belts in the grocery line.

    ReplyDelete
    Replies
    1. useful_idiotApril 16, 2012 at 7:37 AM

      good everyday examples, im not sure about teh conveyor belt being a pulley but i could be wrong and if its not a pulley then what type of machine is it?

      Delete
  10. AnonymousApril 15, 2012 at 11:39 PM

    1. Like the others have said I believe that the higher output increase tHe MA.
    2. Pulleys atelier used in many situtations, such as lifting, and I liked the example of a flagpole from the comments above ^^^
    3. A pulley like this would be use to make a job easier for someone. It could be used to move a heavy object etc.
    - after reading all of the comments, and looking at the pulley , I still feel like I really don't have an understanding of the gears and that rectangular box
    HALIE FOULKS

    ReplyDelete
  11. useful_idiotApril 16, 2012 at 7:33 AM

    1.I believe that the more strings you have going back and forth then the less input force is needed. With a higher output force than input force, you will get a higher mechanical advantage.
    2. pulleys are used in rock climbing and wells to retreive water
    3. i think the triangle and the box are some type of counter that counts how many revolutions the pulley makes

    ReplyDelete
  12. Brian BearssApril 16, 2012 at 7:39 AM

    Useful_idiot,

    I think you're right. My guess is that that "gear" is used to interrupt a beam of light, and that there is a sensor that counts how that light flashes on and off. To me, the rectangular box looks like a USB jack where a cable could be connected to transfer the data to a computer.

    Thanks for all the comments this week.

    ReplyDelete

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