IMA

[Cassidilla]

Can you explain to me exactly what ideal mechanical advantage is, and how do you calculate it? For example, in the rules it states "For a transfer to count for points, both simple machines must use mechanical advantages to transfer energy." I'm having trouble visualizing what this means.

[Unome]

Ideal mechanical advantage is the multiplier determining how much you gain in output force as compared to input force (under ideal conditions, i.e. no friction and similar stuff). It is defined mathematically as:

(Output Force) / (Input Force)

(my LaTeX skills are nonexistent, else that equation would look better). For example, on this lever if the Effort Arm is twice as long as the Load Arm, the IMA is equal to 2; since the total work (in this case torque multiplied by axial distance) must be the same for input and output, if the axial distance on the input side (i.e. how far away from the fulcrum the torque is exerted at, effectively the length of the arm on a simple lever) is twice as large as the axial distance on the output side, the force on the output side must be twice as large as the force on the input side to keep the work on either side equal. This applies to other types of simple machines in a similar way (someone else can describe them specifically, I don't have time right now).

In Mission Possible, what this means is that each transfer must utilize IMA. For example (according to my interpretation of the rule, which could be totally wrong, as I haven't read the rules for this event in a while and have never competed in it), you couldn't use the pulley on the left since it has an IMA of 1, and therefore does not use mechanical advantage to transfer energy (since with an IMA of 1 you gain no force or distance). If you used the center pulley, it would definitely count as using mechanical advantages to transfer energy (so long as you used it properly).

As I said, I haven't read the rules in a while and have never competed in this event, so definitely wait for someone else to respond (I just stepped in to explain the concept of IMA).

[kinghong1970]

a related question...

so in the contest, the simple machines must have IMA > 1 for most part... but do they have to operate utilizing the IMA?

for example:

Effort Arm = 4 cm
Load Arm = 1 cm
IMA = 4

but can the actual load for the running of the simple machine need to have a 10 gram effort lifting a 40 gram load or will it satisfy just to utilize the simple machines with IMA > 1
or to ensure the transfer of events, use a 40gr effort to lift a 40gr load, the IMA added security that it'll work?

thanks.

[Unome]

a related question...

so in the contest, the simple machines must have IMA > 1 for most part... but do they have to operate utilizing the IMA?

for example:

Effort Arm = 4 cm
Load Arm = 1 cm
IMA = 4

but can the actual load for the running of the simple machine need to have a 10 gram effort lifting a 40 gram load or will it satisfy just to utilize the simple machines with IMA > 1
or to ensure the transfer of events, use a 40gr effort to lift a 40gr load, the IMA added security that it'll work?

thanks.

I'm not certain, but I believe that the rules mention that for some types of simple machines (or possibly all types), the IMA must be necessary to complete the task (this is just from memory though).

[juddweeks]

This year there are a lot of requirements to lift an object 10 cm. Are we really saying the object has to be on the load side? For a gun and tackle pulley with an IMA of 2, that would me we would have to move the effort side 20 cm for it to be a scoreable machine. That seems like a lot of movement for a device that is supposed to be less than 60 cm. It would be even worse for more complex pulley systems.

If we can reverse it and use more force to move an object twice as far, aren't we really using the mechanical advantage of the pulleys to our advantage? I got to think that was the intent with the way the rules are written.

I understand that pulleys are typically used to lift heavy things, but in this case the reverse seems legit.

[torqueburner]

This year there are a lot of requirements to lift an object 10 cm. Are we really saying the object has to be on the load side? For a gun and tackle pulley with an IMA of 2, that would me we would have to move the effort side 20 cm for it to be a scoreable machine. That seems like a lot of movement for a device that is supposed to be less than 60 cm. It would be even worse for more complex pulley systems.

If we can reverse it and use more force to move an object twice as far, aren't we really using the mechanical advantage of the pulleys to our advantage? I got to think that was the intent with the way the rules are written.

I understand that pulleys are typically used to lift heavy things, but in this case the reverse seems legit.

The object being lifted is the load, so if you put it on the other side, that side becomes the "load side", and the IMA is only 0.5.

[JZhang1]

a related question...

so in the contest, the simple machines must have IMA > 1 for most part... but do they have to operate utilizing the IMA?

for example:

Effort Arm = 4 cm
Load Arm = 1 cm
IMA = 4

but can the actual load for the running of the simple machine need to have a 10 gram effort lifting a 40 gram load or will it satisfy just to utilize the simple machines with IMA > 1
or to ensure the transfer of events, use a 40gr effort to lift a 40gr load, the IMA added security that it'll work?

thanks.

I am pretty sure that only the pulleys have an IMA requirement, when the rules say mechanical advantages but not IMA, it's intended that the simple machine just has a purpose in general. When the rules say "Both simple machines muse use mechanical advantages", it's just to prevent incidents that occurred last year, for example: a wheel and axle ,or a screw, just rolling down.
All the requirements for each simple machine are defined in 4.d.