Machines B/C

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Re: Machines B/C

Postby Unome » September 4th, 2019, 12:00 pm

Would friction also apply to concepts with pulleys in which friction is generated by the pulley as well as by the weight of the cable/rope? (for div C)
Doing pulley friction without dynamics seems like a limiter on the complexity of such problems (but I haven't looked at pulley friction since the event was last in rotation so I'm not certain).
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Re: Machines B/C

Postby UTF-8 U+6211 U+662F » September 4th, 2019, 5:02 pm

Curiously, rule 4.e forbids tests from asking participants to calculate dynamics. Preventing the calculation of force on objects seems to excise much of the physics behind such a physics event. Perhaps, though, I have misunderstood what this line is saying? My present understanding is that the rule disallows calculation of force for objects not in equilibrium, so students only need to grasp force conceptually. Is anybody able to clarify?
Basically, this rule only allows for calculations dealing with static equilibrium. This doesn't mean, however, that calculations involving motion are banned. If the objects in the system are moving at constant velocities and the net force/torque of the system is zero, then the calculation is allowed. In fact, most scenarios you can think of involving this event should be allowed.

The only questions that wouldn't be allowed (just off the top of the head) would be scenarios specifically dealing with acceleration or oscillating systems, in which case this event would become Hovercraft 2.0 :P.
A system with constant velocity is in dynamic equilibrium, not static equilibrium. (This depends on your frame of reference, but I don't think that's particularly relevant for Machines.)

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Re: Machines B/C

Postby jaggie34 » September 7th, 2019, 8:35 am

How are most people planning on connecting the two levers?
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Re: Machines B/C

Postby annabelle0308 » September 8th, 2019, 1:04 pm

Hi, I'm trying to compile a list of materials for my school to order, so I have a few questions:

What's the best material to make the levers out of?

What hooks/ other materials are needed to construct the device?

Thanks!
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Re: Machines B/C

Postby AlfWeg » September 8th, 2019, 1:11 pm

What's the best material to make the levers out of?
Annabelle
I used wood last time this event came around and it worked well. it's also really easy to manipulate wood, compared to, like, aluminum, imo
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Re: Machines B/C

Postby annabelle0308 » September 8th, 2019, 1:22 pm

What's the best material to make the levers out of?
Annabelle
I used wood last time this event came around and it worked well. it's also really easy to manipulate wood, compared to, like, aluminum, imo
Thank you!

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Re: Machines B/C

Postby IvanGe » September 13th, 2019, 8:35 pm

How are most people planning on connecting the two levers?
string or screws?
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Re: Machines B/C

Postby lvk1157 » September 17th, 2019, 5:58 pm

Does anyone know of good textbooks to use for the test portion of this event?

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Re: Machines B/C

Postby splane21 » September 18th, 2019, 4:58 am

Does anyone know of good textbooks to use for the test portion of this event?
I would probably read Wikipedia and familiarize yourself with the different simple and compound machines. Wikipedia also has all the equations you need, some derivations, and explains concepts pretty well in my opinion. I think the equations and concepts are not that hard it's just finding practice problems. To study energy you could use any good physics textbook like Giancoli, Resnick and Halliday, or University Physics (Young and Freeman). Make sure you understand concepts of Mechanical Advantage, Ideal Mechanical Advantage, Real Mechanical Advantage, etc. really well and know all the equations for each of the simple machines.
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Re: Machines B/C

Postby viditpok » September 21st, 2019, 7:22 am

Since the rules are very vague this year, it is kind of hard for me and my schools machines participants to determine what questions would be asked in these competitions? Can anyone provide questions or a test they have made that will help us understand this event better for this year?


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