Simple Machines B/Compound Machines C

[megamastergamer]

How are you supposed to measure the weight of something with a 1st class lever?

[chinesesushi]

How are you supposed to measure the weight of something with a 1st class lever?

You have a known mass and an unknown mass. By adjusting the positions of the said masses on a lever (that you made), you can determine the unknown mass through applications of MA and Fout and Fin. (you should know how to if you're doing this event)

[caseyotis]

Okay. I'm probably doing this event because no one else wants to/can do it and we're already not doing a lot of events, so I don't want to lose too many points.
Trouble is, I know next to nothing about any of these concepts. And since this is new, the Wiki is not helping a whole lot.
I can learn the historical parts and stuff like that for test. But could someone please try to explain to me the general equations, terminologies, etc. that we have to know? I know it's asking a lot, but I know nothing.

Also, for the building part of it. I want to do this, but I don't even know where to start. At all. I sort of understand a class 1 lever, but the class 2 lever doesn't make sense to me, and how to connect them in series is way over my head. This is probably what I need the most help with because it's so crucial.

For the binder, can we bring in whatever we want? Like, any equations, notes, facts, definitions, etc.?

[chinesesushi]

A compound machine is basically more than one simple machine connected to each other to give a greater overall mechanical advantage. Because this is the definition of a compound machine, all you need to do is make sure you understand the general equations for simple machines and mechanical advantage/efficiency. These are easily found online, so I'll just give a quick overview.
Ideal Mechanical Advantage (IMA) is calculated uniquely depending on which type of simple machine you have. Actual Mechanical Advantage (AMA) is easier to calculate. It is just F(out) / F(in). Efficiency is AMA/IMA * 100%, and is always less than 1 in a non-ideal machine (thus, AMA is always less than IMA).
Levers have 3 classes, class 1, 2, and 3. They differ on the order of the effort (where the force is exerted), fulcrum (essentially the pivot point), and the resistance (the load to be supported). Class 1 levers have the fulcrum between the effort and resistance. Class 2 levers have the resistance between the effort and fulcrum. Class 3 levers have the effort between the resistance and fulcrum. If you need visual support, just look up diagrams online (they'll help). IMA is calculated by the following equation: (distance from effort to fulcrum) / (distance from resistance to fulcrum).
Pulleys are easier to calculate the IMA, as IMA = # of supporting ropes.
The IMA of wheel and axles is just (diameter of wheel) / (diameter of axle).
The IMA of an inclined plane is http://en.wikipedia.org/wiki/Inclined_plane#Terminology .
The IMA of the wedge can also be found online.
The IMA of a screw is the circumference of screw divided by the pitch (length between threads).
In the end, most of these can be found online ( http://iqa.evergreenps.org/science/phy_science/ma.html ).

As for the building part, an example of a class 1 lever connected in series to a class 2 lever ( I explained it above ) would be where the resistance of the class 1 lever is connected to the effort of the class 2 lever. By moving the masses (loads) around you are able to determine the unknown weight by applying principles of mechanical advantage. An example of a machine would be here

PIC (Click to Show Hidden Text)

[img]http://i.imgur.com/cP9dm43.png[/img]

(drew it myself - lol) where the boxes with the arrows are the loads and the triangles are the fulcrums. That theoretically could work (make the levers out of stiff wood, etc.).

I believe you are allowed to bring anything in the binders, as long as it can't fall out.

Hope this helps.

[caseyotis]

Thank you so much! This really helps.

What would be a good building material to use for this?

[chinesesushi]

Thank you so much! This really helps.

What would be a good building material to use for this?

SHORT ANSWER: hardwood.
LONG ANSWER: Basically any type of hardwood (basswood, plywood, you could use hardwood dowels from Michaels). If you have the equipment you could use metal, but depending on the metal it might be more difficult to get an accurate cut. Essentially, any stiff, hard material should be suitable. Don't use a soft one, because the string that holds the mass could cut into the wood, and don't use a bendy one, because the weight might bend the lever and lead to inaccurate measurements (learned this the hard way XD). Make sure to make your levers tall enough because the object can be 15 cm x 15 cm x 15 cm big. And make sure your design conforms to requirements.

[caseyotis]

Thank you so much! This really helps.

What would be a good building material to use for this?

SHORT ANSWER: hardwood.
LONG ANSWER: Basically any type of hardwood (basswood, plywood, you could use hardwood dowels from Michaels). If you have the equipment you could use metal, but depending on the metal it might be more difficult to get an accurate cut. Essentially, any stiff, hard material should be suitable. Don't use a soft one, because the string that holds the mass could cut into the wood, and don't use a bendy one, because the weight might bend the lever and lead to inaccurate measurements (learned this the hard way XD). Make sure to make your levers tall enough because the object can be 15 cm x 15 cm x 15 cm big. And make sure your design conforms to requirements.

Yeah, I'd definitely prefer wood. I don't have any experience with building events, so we'll see how this goes.
Thank you so much for all this help - I really appreciate it.

[ohiostar]

Does anyone know the unknown mass that was used at the Wright State invitational yesterday (C Division)?

[Sciolapedia]

No but I got second place and our estimate was 500.11 grams

[helicpters_rule]

Anyone know the known mass/unknown mass of Wright State for Division B.