## Simple Machines B/Compound Machines C

technomario
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### Re: Simple Machines B/Compound Machines C

Are there different classes of pulleys like levers?
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sunvenu
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### Re: Simple Machines B/Compound Machines C

The rules explicitly indicate that it will include concepts, calculations, and history questions. Are the students expected to answer some of the concept questions in the form of essays? Thanks

chinesesushi
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### Re: Simple Machines B/Compound Machines C

technomario wrote:Are there different classes of pulleys like levers?
Well, the different classes of pulleys are not as explicitly defined as the lever classes. There are two classes, the fixed and movable pulley. The fixed has an MA of 1 and the movable has an MA of 2.
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chinesesushi
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### Re: Simple Machines B/Compound Machines C

sunvenu wrote:The rules explicitly indicate that it will include concepts, calculations, and history questions. Are the students expected to answer some of the concept questions in the form of essays? Thanks
If you mean a full-on essay, I doubt you would have enough time to write the essays and answer all the other questions. However, a short-answer question where you have to write anywhere from a sentence to a paragraph on concepts seems likely. This is all guesswork--since no one knows what the test is like, we can only guess. Good luck!
Never argue with an idiot, they will drag you down to their level and then beat you with experience.
Before you criticize a man, walk a mile in his shoes. That way you'll be a mile away and he'll be shoeless.
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chinesesushi
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### Re: Simple Machines B/Compound Machines C

How would one find the ideal mechanical advantage of a wedge? The only reason I am asking this is because I used to believe it was the side length divided by thickness, according to http://iqa.evergreenps.org/science/phy_science/ma.html, but I recently saw another source that claimed it was the depth of penetration divided by thickness of wedge, according to http://hyperphysics.phy-astr.gsu.edu/hb ... cline.html. Which is correct? Please help!
Never argue with an idiot, they will drag you down to their level and then beat you with experience.
Before you criticize a man, walk a mile in his shoes. That way you'll be a mile away and he'll be shoeless.
You should only create problems, that only you know solutions to.

JustDroobles
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### Re: Simple Machines B/Compound Machines C

chinesesushi wrote:
technomario wrote:Are there different classes of pulleys like levers?
Well, the different classes of pulleys are not as explicitly defined as the lever classes. There are two classes, the fixed and movable pulley. The fixed has an MA of 1 and the movable has an MA of 2.
That's not strictly true. For example, all of these pulleys have one fixed and one movable pulley, but different IMAs.
You should count the number of strings which will change length. The mechanical advantages for these pulleys are 2, 3, 4, 5, and 6 respectively.

chinesesushi
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### Re: Simple Machines B/Compound Machines C

JustDroobles wrote:
chinesesushi wrote:
technomario wrote:Are there different classes of pulleys like levers?
Well, the different classes of pulleys are not as explicitly defined as the lever classes. There are two classes, the fixed and movable pulley. The fixed has an MA of 1 and the movable has an MA of 2.
That's not strictly true. For example, all of these pulleys have one fixed and one movable pulley, but different IMAs.
You should count the number of strings which will change length. The mechanical advantages for these pulleys are 2, 3, 4, 5, and 6 respectively.
I believe I am correct in saying that the pulleys you have listed are not all 2-pulley systems, but rather utilize a sheave of some sort like this (http://sultanvcc.webs.com/23%20three%20 ... rchase.jpg). That's the three-fold purchase that you have in your photo, which is, as you can see, not just two pulleys, but rather multiple pulleys. I was speaking of single pulleys, like a wheel with only one groove.
Never argue with an idiot, they will drag you down to their level and then beat you with experience.
Before you criticize a man, walk a mile in his shoes. That way you'll be a mile away and he'll be shoeless.
You should only create problems, that only you know solutions to.

Joseph Morales12
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### Re: Simple Machines B/Compound Machines C

I'm in division B (simple machines). Does anyone have examples of questions on the test or how exactly to find out the mass of the object they provide I'm new.

hscmom
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### Re: Simple Machines B/Compound Machines C

Gear question: Is the gear ratio driver/driven or driven/driver? I have seen both on the internet. Can't decide what to teach our B team (and never learned it when I was in school!).
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chinesesushi
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### Re: Simple Machines B/Compound Machines C

hscmom wrote:Gear question: Is the gear ratio driver/driven or driven/driver? I have seen both on the internet. Can't decide what to teach our B team (and never learned it when I was in school!).
Would say driver/driven, because IMA is d(in)/d(out), so the input / output. But I'm not necessarily correct. I'm also not sure what you mean by driver or driven. Are you talking about the number of teeth? Or something else?
Never argue with an idiot, they will drag you down to their level and then beat you with experience.
Before you criticize a man, walk a mile in his shoes. That way you'll be a mile away and he'll be shoeless.
You should only create problems, that only you know solutions to.

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