Here we have some questions about experimental errors.
Q1) We want to see how many significant figures have the measure:
0.0009
The number of significant figures is the number of known digits that are not the leading zeros.
Here we can see four leading zeros, and a single-digit different than zero, which is a 9.
Then we have only one significant figure, the 9.
Q2) Here we will use the measure that is the less exact, as the error of that measure may be larger than the smaller significant figures of the other measures.
Then:
31.2 lb + 38.02lb + 45 lb
The worst measure is 45lb, so the smallest significant figure that we should use is the first one at the left of the decimal point, then we need to round the other two measures to the next whole number, we will get:
31 lb + 38 lb + 45 lb = 114lbs
Q3) We know that the measure is 11.5 seconds and the uncertainty of 1.7%, then the uncertainty will be the 1.7% of the above measure:
(1.7%/100%)*11.5 s = 0.1955 s
Notice that our measure has one significant figure after the decimal point, so we need to round the error to the same significant figure.
0.1955 s ≈ 0.2s
Then the measure is:
11.5 s ± 0.20 s
Q4) We have the measure:
312.0 mph ± 3.9 mph.
The percent uncertainty will be the quotient between the error and the measure times 100%, or:
(3.9 mph/312.0 mph)*100% = 1.25%
This is a percent error, we do not need to round this.
If you want to learn more, you can read:
brainly.com/question/17339020
