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Re: Simple Machines B/Compound Machines C

Posted: November 13th, 2013, 2:30 pm
by Tropius Farmers-357
So, I am new to this event and wondering if you should build an adjustable fulcrum, or if you should have one that is in a fixed position. Also, if you were to make an adjustable fulcrum, how specific are the measurements given? Thanks in advance.

Re: Simple Machines B/Compound Machines C

Posted: November 13th, 2013, 4:36 pm
by hscmom
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?
Well, the driver is the gear that is the input. Maybe it's attached to a motor. It's the gear(s) attached to your bike pedals. The driven gear(s) is the output gear. It's on the back wheel of the bicycle.

So, let's say that the driver has 10 teeth and the driven has 40 teeth. The gear ratio is either 4:1 or it is 1:4. Sigh. I've seen different formulae and explanations on the internet.

Re: Simple Machines B/Compound Machines C

Posted: November 13th, 2013, 5:37 pm
by chinesesushi
Well, the driver is the gear that is the input. Maybe it's attached to a motor. It's the gear(s) attached to your bike pedals. The driven gear(s) is the output gear. It's on the back wheel of the bicycle.

So, let's say that the driver has 10 teeth and the driven has 40 teeth. The gear ratio is either 4:1 or it is 1:4. Sigh. I've seen different formulae and explanations on the internet.
To me, it seems that it would depend on which gear you were applying it to. Like, instead of turning the pedals of your bike, what if you turned the wheels? Then the gear in the wheel would become the driver and the gear in the pedals becomes the driven. I guess it depends where you're applying the force, in which the MA would be number of teeth of driven / number of teeth of driver, I believe.

Re: Simple Machines B/Compound Machines C

Posted: November 13th, 2013, 6:06 pm
by chinesesushi
So, I am new to this event and wondering if you should build an adjustable fulcrum, or if you should have one that is in a fixed position. Also, if you were to make an adjustable fulcrum, how specific are the measurements given? Thanks in advance.
I would think I would build one with adjustable fulcrums because it gives a higher range of measurable mass. The specificity of the measurements depends on your design.

Re: Simple Machines B/Compound Machines C

Posted: November 16th, 2013, 7:23 pm
by helicpters_rule
Hey I am wondering what’s people think about the beam length in rule 3a does the beam go from the fulcrum to the end or the length of the lever?

Re: Simple Machines B/Compound Machines C

Posted: November 16th, 2013, 11:25 pm
by chinesesushi
Hey I am wondering what’s people think about the beam length in rule 3a does the beam go from the fulcrum to the mass or from length of the lever?
Length of lever

Re: Simple Machines B/Compound Machines C

Posted: November 25th, 2013, 4:33 pm
by helicpters_rule
I don't know if anyone said this but a great place to start is the naval course on the national simple machine web page and its interesting.

Re: Simple Machines B/Compound Machines C

Posted: November 25th, 2013, 4:45 pm
by helicpters_rule
Just wondering what type of accuracy on there lever other people are getting on my practice test i get around 20-25 seconds and get usually less then 1 percent error.

Re: Simple Machines B/Compound Machines C

Posted: November 26th, 2013, 8:09 pm
by helicpters_rule
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!
I don't know but most of the sources I have seen have been like http://hyperphysics.phy-astr.gsu.edu/hb ... cline.html so i think it that is the correct calculation and i am almost 100% sure its right. I hope that helps but if I am wrong someone please correct me.

Re: Simple Machines B/Compound Machines C

Posted: November 26th, 2013, 8:13 pm
by helicpters_rule
So, I am new to this event and wondering if you should build an adjustable fulcrum, or if you should have one that is in a fixed position. Also, if you were to make an adjustable fulcrum, how specific are the measurements given? Thanks in advance.
I would think I would build one with adjustable fulcrums because it gives a higher range of measurable mass. The specificity of the measurements depends on your design.
I used a fixed fulcrum because it was easy and the results i got have been pretty good but the moving fulcrum seams like something fun to try but for the event you can only have a certain range and ratio of the masses.