Machines B/C

[Adi1008]

Machines B/C: Teams will complete a written test on simple and compound machine concepts and construct a lever-based measuring device prior to the tournament to determine the ratio between two masses.

Simple Machines Wiki | Complex Machines Wiki

Simple Machines Test Exchange 2015 | Compound Machines Test Exchange 2015

Past Threads: 2014, 2015

Past Question Marathons: 2014, 2015

[gz839918]

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?

[nicholasmaurer]

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?

I'll leave the exact distinction between statics and dynamics to someone with a more rigorous physics background, but I think there are plenty of force calculations relevant to a system at equilibrium... You can still calculate each force even if the net force on the object is zero.

[cool hand luke]

No dynamics doesn't mean there is no force. I recall a statics class that had lots of force calculations. Every building is static, but someone better calculate the forces.

[AlfWeg]

You can still calculate each force even if the net force on the object is zero.

AP Physics has a short chapter on forces at equilibrium, it’s fairly simple tho. (Sample problem: You have diving board at equilibrium, and you know some of the forces, but don’t know others, so u have to set up the equations for torque and forces in the y direction)
Also, physicsclassroom website is great- look up “equilibrium and static’s”. I’m not gonna put the website, cuz I’m not sure of the rules surrounding that.... but it gives u good detail

I’m not sure this is what ur looking for...so Srry if it’s not

[Justin72835]

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 .

[gz839918]

I apologize if I was confusing in what I originally said. You all are correct to note that statics involves force calculations too, but forbidding dynamics was a surprise to me. Often, problems about simple and compound machines involve nonzero net forces (e.g. block moving on an incline, accelerating Atwood machine), so if the rules really mean that only statics but not dynamics may be tested, event supervisors will be restricted on how much physics they have, although for the same reason we can look forward to at least a few very creative tests that go extremely in depth on just statics instead of testing The Usual Stuff about dynamics. Personally, I don't feel that has to be a bad thing although I probably will never gather the inner strength to write such an innovative test oops haha lol

[AlfWeg]

Often, problems about simple and compound machines involve nonzero net forces (e.g. block moving on an incline, accelerating Atwood machine),[/size]

Wait, ur so right. There are so many problems with non-zero forces like that.

[chalker]

As Nick previously alluded to, it's standard within the physics / mechanical engineering communities to make a general distinction between Statics and Dynamics. Just about every college of engineering will introduce students first to Statics concepts via one or a series of classes, which are then followed up by Dynamics classes. Please keep in mind that while some Dynamics concepts could be covered by some So participants, we have to think about the broad base of students and teachers. Hence, sticking with the traditional educational divisions between these 2 makes sense. And there are PLENTY of topics and questions that can be asked just within the Statics realm.

For more details, check out the wikipedia page, which is always a good starting point: https://en.wikipedia.org/wiki/Statics and https://en.wikipedia.org/wiki/Analytical_dynamics if you are interested in the types of stuff NOT included in the event.

[JoeyC]

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)