Name: measurement precision and significant figures
Uploaded: 2023-04-30T10:48:20.000Z
Duration: 1 min 44 s
Channel: JoVE

A certeza da medição depende de dois fatores: o número de dígitos na medição e a precisão do instrumento utilizado.
Em uma quantidade medida, todos os dígitos, incluindo o último dígito incerto, são chamados de algarismos significativos - e podem ser determinados usando regras específicas.
Quaisquer dígitos diferentes de zero e todos os zeros cativos - que ficam entre dois dígitos diferentes de zero - são significativos. Por exemplo, 28 tem dois algarismos significativos, enquanto 26,25 tem quatro e 208 tem três.
Os zeros à esquerda nunca são significativos, pois apenas localizam o ponto decimal. Por exemplo, 0,00208 tem três algarismos significativos. Tais quantidades podem ser expressas usando notações exponenciais. Assim, 0,00208 pode ser escrito como 2,08 × 10−3.
Os zeros à direita são significativos apenas em números formatados com decimal. 2200 tem dois zeros à direita e dois algarismos significativos, enquanto 2200.0 e 2200.1 têm 5 algarismos significativos.
Para quantidades sem pontos decimais, o significado dos zeros à direita torna-se ambíguo. Assim, 2200 pode ser escrito como 2,2 × 103 com dois algarismos significativos ou 2,20 x 103 com três algarismos significativos.

regras para algarismos significativos

Em qualquer medição, a precisão da ferramenta de medição é um fator essencial. Uma régua comum, por exemplo, pode medir comprimentos até o milímetro mais próximo; um paquímetro, por outro lado, pode medir comprimentos até o centésimo de milímetro mais próximo. Como resultado, o paquímetro é uma ferramenta de medição mais precisa, pois pode medir mudanças extremamente pequenas no comprimento. As medidas serão mais exatas se a ferramenta de medição for mais precisa.

Deve-se enfatizar que, ao representarmos valores medidos, o último dígito foi calculado de alguma forma pela pessoa que fez a medição. Por exemplo, uma pessoa que mede o comprimento de um bastão com uma régua percebe que ele parece estar entre 13,2 cm e 13,3 cm e, portanto, deve estimar o valor do último dígito. A regra dos algarismos significativos é que o último dígito anotado em uma medida é o primeiro dígito com alguma incerteza. Comece com o primeiro valor medido à esquerda e conte o número de dígitos até o último dígito escrito à direita para determinar o número de algarismos significativos em um valor. Os algarismos significativos representam a precisão da ferramenta de medição usada para medir um valor.

Este texto foi adapatado de <a href="https://openstax.org/books/university-physics-volume-1/pages/1-6-significant-figures">Openstax, University Physics Volume 1, Section: 1.6 Significant Figures. </a>

Regras para Algarismos Significativos

Em qualquer medição, a precisão do instrumento de medição é um fator essencial. Uma régua comum, por exemplo, pode medir o comprimento até o mais próximo ...

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Rules for Significant Figures

measurement precision and significant figures

Measurement precision depends on the tool used, and significant figures show that precision. A ruler can measure length to the closest millimeter. A caliper can measure length to the nearest 0.01 mm, so it gives a more precise measurement because it can detect very small changes in length.

When a value is written from a measurement, the last digit is not exact. The person making the measurement must estimate that digit. For example, a stick that seems to fall between 13.2 cm and 13.3 cm must be recorded with a guessed last digit.

The last digit in a measurement is the first digit with some uncertainty. To find the number of significant figures, start with the first measured value on the left and count through the last digit written on the right. Significant figures show how precise the measuring tool was when the value was recorded.

Measurement Precision and Significant Figures

measurement-precision-and-significant-figures

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Measurement precision depends on the tool used, and significant figures show that precision. A ruler can measure length to the closest millimeter. A caliper can measure length to the nearest 0.01 mm, so it gives a more precise measurement because it can detect very small changes in length. When a value is written from a measurement, the last digit is not exact. The person making the measurement must estimate that digit. For example, a stick that seems to fall between 13.2 cm and 13.3 cm must...

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Learn how ruler and caliper precision affects measurements and how to count significant figures from the first measured digit to the uncertain last digit.

Measurement Precision and Significant Figures | JoVE K12

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Measurement Precision and Significant Figures

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