#7 - Inertia affects the flow of water pumped through a

[srcline@noctrl.edu]

Hello,

So I'm having a hard time understanding 7. I eliminated D and E, and C to me seems like its twisting the entire premise around. So this is a strengthen question correct? When I was reading the premise it seemed like the author was trying to compare the affects of water flow to electrical circuits, and inertia is used to connect that idea. That was the reason I choose B, especially since the last sentence says " The effects of inductance in electrical circuits are similar to the effects of inertia on water pipes.

Further, I dont see how the "rate" as brought up in a.c. A is relevant in strengthening the idea that somehow water and electrical circuits are similar.

Thankyou
Sarah

[Adam Tyson]

The last sentence of the stimulus sets up a comparison, Sarah, not unlike some you may have seen on other standardized tests such as the SAT. Here, that comparison is:

Inductance is to Electrical Circuits as Inertia is to Water Pipes

If that comparison is valid, then inductance must have an effect on electrical circuits that is analogous to the effect inertia has on water pipes. We know from the stimulus that inertia affects the flow of water through the pipes, because that is exactly what the first sentence says. Therefore, it is reasonable to deduce that inductance affects the flow of current through electrical circuits.

Answer choice B mixes the two things together, putting inertia into electrical currents. That would be just the same as saying the inductance is somehow involved in the flow of water through water pipes! Imagine another comparison like the one in the stimulus:

Chocolate provides the key flavor in chocolate cake. Apples play a similar role in apple pie.

Now,based on this, would you say that chocolate cake requires apples? Of course not! But that is exactly what answer B does, mixing up the two sides of the comparison in a way that is unsupported and nonsensical. Instead, we should look for an answer that says apples provide the key flavor in apple pie, which is what answer A does for us.

I hope that was a useful analogy for you. If not, at least it was a tasty one! Bon appetit!

[srcline@noctrl.edu]

Hello Adam

Okay, that cleared up alot.....at first did see the comparison, but my mistake was in interpreting the first sentence in thinking that :inertia affects the flow of water".... as B. the flow of electrical current in circuit REQUIRES inertia....like you demonstrated in your analogy this doesn't have anything to do with the effects of inductance.

Thankyou
Sarah

[1800-HELPME]

Hello,

I believe this is a Must Be True, not a Strengthen question!

I think I understand why (A) is correct, but I'm not sure why (E) is wrong.

I chose (E) because it says that when the pump is switched off, inertia causes the decrease in the water flow to be gradual, so I thought it would still pump water for a second or two.

I guess it doesn't pass the Fact Test?

[Jonathan Evans]

Hi, HelpMe,

You are correct. This is a Must Be True question. We are using information in the stimulus to prove a statement in an answer choice.

Let's clarify why (A) passes the Fact Test™: If the effects of inductance on electricity is "similar to the effects of inertia" on water, then we have excellent evidence that inductance affects the rate of the electrical current. Why? Because, just as Adam wrote above, all the other evidence in the stimulus backs up the idea that inertia affects the rate of the flow of water.

Is this clear?

With respect to (E), yes, you are correct. It does not pass the Fact Test. We have no evidence to suggest whether or not the pump continues to operate after being switched off. Remember, (E) may very well be true in real life. However, we simply have no evidence for it in the stimulus. It is an excellent example of a "Could Be True" incorrect answer to a Must Be True question.

I hope this helps!

[lsnewbie]

Hello PS,
Could you please tell me why answer choice C is wrong? I was stuck between that and answer choice A. I went with C because I gathered, based on the question, that in the same way that inertia affects the flow of water in pipes, inductance affects the electric flow in circuits and so put the two together to assume that an electric pump would work through inductance - was I wrong to think so? I see why A is a better answer choice since it is better supported by the premise for a MBT question, while C is perhaps unsupported (outside the scope, maybe?) … would appreciate some clarification.
Thanks!
JT

[Adam Tyson]

You already got it, JT - C is wrong because A is better, and because C is outside the scope. There is no information in the stimulus to allow us to conclude that inertia in the pipes is caused by inductance in the pumps. Maybe it's caused by something to do with mass and physics that have nothing to do with what's happening in the circuits? C is just trying to confuse us by mashing the two ideas together.