A student makes measurements from which she calculated the speed of sound as 321 ms-1 . She estimates that the result is accurate to +3% or -3% . Which of the following give results expressed to the appropriate number of significant figures?
Correct answer: A. 327 ms-1
- A. 327 ms-1
- B. 328 ms-1
- C. 330 ms-1
- D. 300 ms-1
Explanation
a) 327 m/s:This option provides a result with three significant figures. However, the given measurement is accurate to +3% or -3%, which means the uncertainty in the measurement is ±3%. Therefore, the appropriate number of significant figures should consider the uncertainty, and in this case, it should be expressed as 321 ± 3 m/s. Rounded to three significant figures with the appropriate uncertainty, it would be written as 321 ± 3 m/s.
This question appeared on the HEC Phase II 2017 paper, which you can sit online with every answer explained.
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About Errors and Significant Figures
Measurement errors include random and systematic effects, absolute, fractional and percentage uncertainty, and the precision shown by significant figures. Questions apply rounding rules and uncertainty propagation in addition, subtraction, multiplication and division, while distinguishing accuracy from precision and uncertainty from an actual mistake.
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