Name: si units for physical quantities
Uploaded: 2023-04-30T10:47:50.000Z
Duration: 1 min 10 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Physical Science

PS.1

PS.1.b

Units and Standards of Measurement

Uma grandeza física é qualquer número que descreve um fenômeno físico quantitativamente. Por exemplo, comprimento é uma quantidade física que descreve a distância entre dois pontos.
As medidas das grandezas físicas são expressas em termos de unidades. A massa do seu corpo pode ser expressa em quilogramas e sua altura em metros.
As grandezas físicas expressas sem unidades padrão são difíceis de entender. Por exemplo, se a altura da Torre Eiffel for relatada como 300, sem fornecer unidades, o contexto do número não é claro. Isso significa que a torre Eiffel pode ser relativamente alta ou muito baixa.
A fim de medir e relatar as várias propriedades da matéria com precisão, um sistema comum de medição foi desenvolvido conhecido como Sistema Internacional de Unidades ou unidades SI.
O sistema SI recomenda o uso de sete quantidades básicas e suas unidades, que formam o Sistema Internacional de Quantidades.

unidades e padrões de medição

Uma quantidade física pode ser definida especificando seu método de medição ou indicando como ela é calculada a partir de outras medidas. Por exemplo, considere um cubo metálico. Poderíamos definir sua massa e dimensões especificando os métodos para medi-los, como usar uma balança e uma régua. Em seguida, poderíamos definir o volume dizendo que é o cubo do seu lado, e poderíamos calcular a densidade como a massa dividida pelo volume.

Medições de quantidades físicas são expressas em termos de unidades, que são valores padronizados. Por exemplo, o comprimento do lado de um cubo, que é uma quantidade física, pode ser expresso em unidades de metros ou centímetros, dependendo do tamanho do cubo.

Existem dois sistemas principais de unidades em uso. O primeiro é o sistema métrico, que utiliza unidades do SI, e o segundo é o sistema imperial, que utiliza unidades inglesas. SI é a abreviação internacional para o Sistema Internacional de Unidades. Ele é o sistema de unidades mais amplamente utilizado globalmente, sendo considerado o sistema padrão por cientistas e matemáticos.

Este texto foi adaptado de <a href="https://openstax.org/books/university-physics-volume-1/pages/1-2-units-and-standards">Openstax, University Physics Volume 1, Section 1.2: Units and Standards.</a>

Unidades e padrões de medição

Uma grandeza física é definida especificando seu método de medição ou declarando como ela é calculada a partir de outras medições. Por exemplo...

Education

JoVE Core

Physics

Física

Unit 1

Unidade 1

Units, Dimensions, and Measurements

Unidades, Dimensões e Medidas

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

si units for physical quantities

SI units give a standard way to measure physical quantities. A physical quantity can be defined by how it is measured or by how it is calculated from other measurements. For example, the mass and dimensions of a metallic cube can be found with a weighing machine and a meter scale.

Some quantities are built from others. The volume of a cube is the cube of its side length. The density of the cube is then found by dividing mass by volume.

Measurements are written in units, which are standardized values. The same length can be expressed in meters or centimeters, depending on the size of the object. Two main unit systems are used in science and everyday life. The metric system uses SI units, while the customary or imperial system uses English units.

SI is the abbreviation for the French name Système International d'Unités. It is the most widely used unit system in the world. Scientists and mathematicians consider it the standard system.

SI Units for Physical Quantities

the scope of physics

How Physics Shapes Science and Technology

Physics studies the interactions of energy, matter, space, and time. It looks for the basic mechanisms that explain natural phenomena. The word physics comes from the Greek word physis, which means nature. Physics helps us understand the natural world at its most fundamental level. It relies on quantitative laws, or rules written in numbers and measurements, to describe how things behave. That approach can also help other fields improve the limits of current technology. Physics matters in...

orders of magnitude

Estimating Scale with Powers of 10

Orders of magnitude help estimate the scale of a number using powers of 10. It is a simple way to round values to the nearest power of 10. This makes it easier to compare very large and very small numbers. To find the order of magnitude of a number, take its base-10 logarithm and round to the nearest integer. The result gives the power of 10 that most closely matches the original value. This method gives a consistent estimate of size without using exact digits. Orders of magnitude are useful...

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models, theories, and laws

Scientific Models, Theories, and Laws

Scientific models, theories, and laws help physicists describe natural phenomena. A model is a simplified version of a physical system that is too complex to study in full. It acts as a rough mental or visual picture of what may be happening. Good models keep the important parts and simplify the rest so the problem becomes workable. The light wave model is one example. Light waves are usually invisible, so they cannot be seen in the same way as water waves. Even so, it is useful to think of...

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units and standards of measurement

SI units give a standard way to measure physical quantities. A physical quantity can be defined by how it is measured or by how it is calculated from other measurements. For example, the mass and dimensions of a metallic cube can be found with a weighing machine and a meter scale. Some quantities are built from others. The volume of a cube is the cube of its side length. The density of the cube is then found by dividing mass by volume. Measurements are written in units, which are standardized...

estimation of the physical quantities

Fermi Estimation for Physical Quantities

Fermi estimation helps physicists, scientists, and engineers make rough calculations for physical quantities. These estimates are also called guesstimates, order-of-magnitude approximations, back-of-the-envelope calculations, or Fermi calculations. Enrico Fermi was known for making these kinds of estimates with surprising precision. Estimation is not random guessing. It uses prior experience and sound physical reasoning to get a rough value for a quantity. This kind of reasoning helps build...

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base quantities and derived quantities

SI Base Units Behind Measured Quantities

SI base units are the starting point for measuring physical quantities. In any system of units, some quantities must be defined through direct measurement. These are called base quantities, and their units are base units. Other physical quantities are built from these base values by algebraic combinations. These are called derived quantities, and their units are derived units. For example, area comes from two lengths multiplied together. It is a derived quantity and is written in SI base units...

conversion of units

Unit Conversion Steps and Real-World Errors

Unit conversion lets you change a measurement from one unit to another. It is useful in everyday life, such as when a cookbook gives amounts in liters or ounces and you need cups instead. It also helps when directions use feet or meters, but you want to know the distance in miles. The first step is to list the given unit and the unit you need. The second step is to choose a conversion factor, which is a ratio that shows how many of one unit equal another unit. For example, 1,000 meters equal 1...

accuracy and precision

Repeated Measurements in Science

Repeated measurements help scientists check the quality of their results. They are used to judge both precision and accuracy. These two ideas are related, but they do not mean the same thing. Measurements are precise when repeated trials give very similar results. Precision shows how closely the values agree with one another. Measurements are accurate when the result is very close to the true value or the accepted value. Accuracy shows how closely the values agree with the real target. High...

random and systematic errors

How Measurement Errors Affect Results

Measurement errors can change how accurate and precise a result appears. Scientists try to record measurements as carefully as possible, but errors can still happen. These errors are usually random or systematic. Random errors come from inconsistency or fluctuation in the measuring process. They can also come from changes in the quantity being measured. In repeated measurements, random error may make a value appear greater than the true value one time and less than it the next. A simple...

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...

significant figures in calculations

Rounding Rules for Significant Figures

Rounding rules for significant figures help show the right level of certainty in measured results. When a calculation is reported with the correct number of significant figures, it better matches the uncertainty in the measurements. The rounding rule depends on the type of math being done. For addition and subtraction, the result should have the same number of decimal places as the number with the fewest decimal places. For multiplication and division, the result should have the same number of...

dimensional analysis

Dimensional Checks in Physics Equations

Dimensional consistency is a key check in physics equations. It means the dimensions on both sides of an equation must match. The idea helps show whether an equation can represent a real physical law. The first rule is simple: expressions on each side of the equal sign must have the same dimensions. That makes sense because you can only add or subtract quantities of the same type. The second rule says that the input to a standard mathematical function, such as a trigonometric function, a...

problem solving: dimensional analysis

Dimensional Checks for Physics Equations

Dimensional analysis helps check whether physics equations make sense. It compares the dimensions on each side of an equation and shows whether the units are consistent. This method is useful for spotting algebra errors, typos, and for remembering physical laws. A valid equation must follow two rules. First, both sides of an equality must have the same dimension, so only quantities with matching dimensions can be added or subtracted. Second, common math functions such as exponential,...

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solving problems in physics

Physics Problem Solving: Strategy to Check

Physics problem solving uses general physical principles to work out specific situations. It is a key skill in physics, and it can also help with everyday life. The same analytical skills can be used in new situations, while a list of facts can never cover every possible case. Solving physics problems also takes creativity and insight. These skills grow with experience and practice. There is no simple step-by-step method that works for every problem, but a three-stage process can guide the...

key terms and concepts

Learn how physical quantities are measured with standardized units, including SI, metric, and English units, plus cube examples of volume and density.

SI Units for Physical Quantities | JoVE K12

physics

JoVE Core - Fisica apresenta a teoria e a aplicação de tópicos fundamentais da física, incluindo cinemática, dinâmica, mecânica dos fluidos, estática, ondas e acústica, com vídeos animados concisos e de fácil compreensão. Além disso, os vídeos de cientistas em ação demonstram a aplicação de conceitos relacionados em experimentos de pesquisa clássica e original realizados nos laboratórios de todo o mundo hoje em dia.

PH.1

PH.1.b

Texas Essential Knowledge and Skills

High School

Chemistry

CHEM.1

CHEM.1.E

Alabama Course of Study Science

9-12

Earth and Space Science

Earth's Place in the Universe

9-12.ESS.1.2.b

PHYS.1

PHYS.1.E

Chemistry and Physics

IPC.1

IPC.1.E

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• offer simple solutions to design problems

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The student will demonstrate an understanding of scientific and engineering practices by planning and carrying out investigations
• independently and collaboratively plan and conduct observational and experimental investigations; identify variables, constants, and controls where appropriate and include the safe use of chemicals and equipment
• evaluate the accuracy of various methods for collecting data
• take metric measurements using appropriate tools and technologies
• apply scientific ideas or principles to design, construct, and/or test a design of an object, tool, process or system

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The student will demonstrate an understanding of scientific and engineering practices by pnterpreting, analyzing, and evaluating data
• construct and interpret data tables showing independent and dependent variables, repeated trials, and means
• construct, analyze, and interpret graphical displays of data and consider limitations of data analysis
• apply mathematical concepts and processes to scientific questions
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PS.1.c

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Deductive Reasoning

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The student will demonstrate an understanding of scientific and engineering practices by constructing and critiquing conclusions and explanations
• construct scientific explanations based on valid and reliable evidence obtained from sources (including the students' own investigations)
• construct arguments supported by empirical evidence and scientific reasoning
• generate and compare multiple solutions to problems based on how well they meet the criteria and constraints
• differentiate between a scientific hypothesis, theory, and law

PS.1.d

The student will demonstrate an understanding of scientific and engineering practices by developing and using models
• construct, develop, and use models and simulations to illustrate and/or explain observable and unobservable phenomena
• evaluate limitations of models

PS.1.e

SI Units for Physical Quantities

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