# Science- Ms. Sue or DrBob222?

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A student measures a rectangular room to be 20.0 m X 17.16 m. Which of the numbers below represents the room’s area with the correct number of significant figures?
a. 340 m^2
b. 343 m^2
c. 343.2 m^2
d. 343.20 m^2

B

Which component of the technological system is activated when an automobile airbag inflates?
a. input
b. feedback
c. process
d. output

D

a. Knowing the main ideas ahead of time helps you know where to focus your attention.
d. Surveying ahead of time means you can skip maps, diagrams, and content summaries later.

A

A student measures the mass of a paper clip. The student’s data table is shown below. The accepted value for the paper clip’s mass is 1.14 g.
Trial 1, 2.45 g
Trial 2, 2.40 g
Trial 3, 2.42 g
Which of the following describes the student’s measurements?
a. The student’s measurements were accurate, but not precise.
b. The student’s measurements were precise, but not accurate.
c. The student’s measurements were neither precise nor accurate.
d. The student’s measurements were both precise and accurate.

B

• Science- Ms. Sue or DrBob222? -

• Science- Ms. Sue or DrBob222? -

Thanks!

Just to make sure...for the first one, 343.2 is rounded to 343 so that there are 3 significant figures. For the second one, is the input for the airbag inflation the crash?

• Science- Ms. Sue or DrBob222? -

Yes, 343.2 must be rounded to 3 s.f.
I think the crash is the input.

With regard to the last one I'm not so sure I would go with B. It's a little difficult to know because we don't know what the asker considers precise and or accurate. Certainly the accuracy is no good by any set of standards. Also, we don't know what kind of balance was used to determine the mass of the paper clip. If I used an analytical balance that measures to 0.1 mg, it is neither accurate nor precise (differences of 20 and 50 mg are not very close compared to 0.1 mg). However, if we used a triple beam balance I believe it can weigh to the nearest 10 mg so 20 mg and 50 mg is not so bad. Having said all of that I think the "feeling" I get from the question is to go with answer B. Surely the asker didn't expect that kind of analysis of the problem.

• Science- Ms. Sue or DrBob222? -

My lesson says that accuracy is how close a measurement (the values of the trials in this case) is to an accepted value (1.14). It also says that precision is how close the measurements are to each other. So, in this case, the student's measurements are close to each other, but not to 1.14. Probably it is b.

Thank you for your help once again!

• Science- Ms. Sue or DrBob222? -

Your lesson is right on both but they don't give any idea of how close is close. So they are right generally but no help when it comes down to the nitty gritty. If I weigh with an analytical balance I expect my measurement to come out, for a paper clip weighing 1.14g---wait, I think I just see it. With a mass of 1.14g they give you the mass 1.14 and you know it should be within 1.13 to 1.15 or 20 mg range.
The average of the three weighings is 5.42 so I might be tempted to change my mind and go with c since the deviation from the average is 30 mg. However, I still think b is the answer the problem is looking for. If you find out I would be interested in knowing the answer the asker expects.

• Science- Ms. Sue or DrBob222? -

An "intuitive" reasoning is what they expect. The word "close" isn't very specific, but looking at the differences between the values:

1. There is a maximum .05 gram difference in the student's measurements.

2. 2.40 (the lowest measurement) - 1.14 = 1.26.

Looking at .05 and 1.26, 1.14 would not be intuitively close.

Most of the questions I get use reasoning to figure out the answer. I'm sure they wouldn't be so specific about how it is measured. B is the type of answer they expect, although going deep into it, c might be correct.

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