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A rule of thumb in designing experiments is to avoid using a result that is the small difference between two large measured quantities. In terms of uncertainties in measurement, why is this good advice?

Short Answer

Expert verified
In summary, using a result that is a small difference between two large measured quantities in experiments is not advisable due to the propagation of uncertainties. The uncertainties in each of the individual measurements combined can lead to a disproportionately large uncertainty in the difference itself. This makes the result less reliable and more prone to inaccuracies. Therefore, avoiding such scenarios helps minimize the impact of uncertainties in measurement, resulting in more accurate and reliable experimental conclusions.

Step by step solution

01

Understanding uncertainties in measurement

Uncertainties in measurement are inherent in any experimental process and are a result of various factors, such as the accuracy and precision of measuring instruments or human error. When interpreting experimental results, it is important to consider these uncertainties to ensure that the conclusions drawn from the results are valid and reliable.
02

Considering the small difference between two large values

When a result is given as the small difference between two large measured quantities (e.g., A - B, where A and B are large values), the uncertainties in both A and B come into play. This is because the uncertainty in the difference depends on the uncertainties in both of the individual measurements.
03

The propagation of uncertainties

The propagation of uncertainties is the process through which the uncertainties of individual measurements affect the uncertainty of the overall result. In the case of the small difference between two large measured quantities, we can analyze the propagation of uncertainties through the formula for the difference: \( \Delta(A - B) = \sqrt{(\Delta A)^2 + (\Delta B)^2} \) Here, Δ(A - B) represents the uncertainty in the difference, while ΔA and ΔB represent the uncertainties in the individual measurements A and B, respectively.
04

Analyzing the impact of the small difference between large values on uncertainty

From the propagation of uncertainties formula, we can see that if A and B are large values with significant uncertainties, then the combined uncertainty in their difference is even larger. Consequently, the ratio of the uncertainty in the difference to the difference itself becomes large, leading to a less reliable result. Essentially, the small difference between two large measured quantities will have a disproportionately large uncertainty, making it difficult to draw accurate conclusions from the result due to higher levels of uncertainty. In conclusion, avoiding the use of results that are small differences between two large measured quantities in experiments is good advice because it helps minimize the impact of uncertainties in measurement. By following this rule of thumb, experiment designers can ensure that the overall uncertainty in the result is kept low, leading to more reliable and accurate conclusions from the experiment.

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Most popular questions from this chapter

You go to a convenience store to buy candy and find the owner to be rather odd. He allows you to buy pieces in multiples of four, and to buy four, you need \(\$ 0.23 .\) He only allows you to do this by using 3 pennies and 2 dimes. You have a bunch of pennies and dimes, and instead of counting them, you decide to weigh them. You have \(636.3 \mathrm{~g}\) of pennies, and each penny weighs \(3.03 \mathrm{~g}\). Each dime weighs \(2.29 \mathrm{~g}\). Each piece of candy weighs \(10.23 \mathrm{~g}\). a. How many pennies do you have? b. How many dimes do you need to buy as much candy as possible? c. How much should all these dimes weigh? d. How many pieces of candy could you buy? (number of dimes from part b) e. How much would this candy weigh? f. How many pieces of candy could you buy with twice as many dimes?

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The density of an irregularly shaped object was determined as follows. The mass of the object was found to be \(28.90 \mathrm{~g} \pm 0.03 \mathrm{~g}\). A graduated cylinder was partially filled with water. The reading of the level of the water was \(6.4 \mathrm{~cm}^{3} \pm 0.1 \mathrm{~cm}^{3}\). The object was dropped in the cylinder, and the level of the water rose to \(9.8 \mathrm{~cm}^{3} \pm 0.1 \mathrm{~cm}^{3}\). What is the density of the object with appropriate error limits? (See Appendix 1.5.)

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