Name: si units and metric prefixes
Uploaded: 2023-09-22T11:49:19.000Z
Duration: 1 min 29 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Specialised Topic in Science

112.51.c.1.

112.51.c.1.E.

International System of Units

מערכת היחידות הבינלאומית מקובלת ברחבי העולם, ויחידות הבסיס הן מטרים, קילוגרמים ושניות. יחידות אלה הן מוחלטות, וערכן אינו משתנה בהתאם למיקום.
קידומות משמשות להגדרת כמויות גדולות יותר וקטנות יותר. מילי, מיקרו וננו משמשים לציון כמויות קטנות יותר, בעוד קילו, מגה וג'יגה משמשים לציון כמויות גדולות יותר.
עם זאת, מבין יחידות הבסיס, הקילוגרם הוא יחידת הבסיס היחידה המוגדרת עם קידומת.
יש להקפיד על כמה כללים בעת הבעת יחידות וקידומות. ראשית, נקודות משמשות להבדיל בין יחידות ביחידות מרוכבות.
שנית, נמנעת קידומת במכנה ומתבטאת רק בנומרטור של היחידה המרוכבת.
שלישית, הכוח המעריכי על יחידה עם קידומת חל על הקידומת והיחידה שלה, ולבסוף, התוצאה מיוצגת באמצעות קידומת אחת.
בניגוד למערכת המטרית, SI אינו משתמש בכפולות של deca או centi.

<ol>
	<li>היבלר, R.C. (2016). מכניקה הנדסית - סטטיקה ודינמיקה. הובוקן, ניו ג'רזי: אולם פירסון פרנטיס. עמ' 9\u201210</li>
	<li>באר, פ"פ; ג'ונסטון, א.ר.; מזורק, ד"ו; קרומוול, פי ג'יי ועצמי, ב. (2019). מכניקה וקטורית למהנדסים - סטטיקה ודינמיקה. ניו יורק: מקגרו-היל. עמ' 5 ו-7</li>
	<li>מרים, י"ל; Kraige, L.G. ובולטון, J.N. (2020). מכניקה הנדסית - סטטיקה. הובוקן, ניו ג'רזי: ג'ון ווילי. עמ' 7 ו-8</li>
</ol>

מערכת היחידות הבינלאומית

<div style="direction:rtl">מערכת היחידות הבינלאומית, שידועה גם בשם מערכת ה-SI, היא מערכת מדידה שמקובלת ומשמשת בכל רחבי העולם. מערכת ה-SI מבוססת על מערך של שלושה יחידות בסיס, שנחשבות למוחלטות, וערכיהן אינם משתנים בהתאם למיקום. היחידות הבסיסיות הללו הן מטרים, קילוגרמים ושניות. תחילה נעשה שימוש בקידמות כדי להגדיר כמויות גדולות וקטנות במערכת ה-SI. לדוגמה, מילי, מיקרו וננו מגדירות כמויות קטנות, גודלי קילו, מגה וגיגה משמשות כדי להגדיר כמויות גדולות יותר. הקילוגרם הוא היחידה הבסיסית היחידה המוגדרת עם קידמה בין יחידות הבסיס של מערכת ה-SI. ישנן מספר חוקים שיש להקפיד עליהם בעת ביטוי יחידות וקידמות. ראשית, יש שימוש בנקודות כדי להבדיל בין יחידות מרוכבות. שנית, מנוצל הקידום והוא לא נמצא במכנה ולאחריו מבטאים יחידה מרוכבת. שלישית, כוח אקספוננציאלי על יחידה מרוכבת עם קידום מתייחס לקידום והיחידה שלו. במילים אחרות, התוצאות מיוצגות בעזרת יחידה אחת. חשוב לציין שמערכת ה-SI אינה משתמשת בכפלי דיקה או מאות שלא כמו המערכת המטרית. הקידמות של מערכת ה-SI מבוססות על כוחות של עשרה, עם היחידה הבסיסית ללא קידום. ביחידות ה-SI ניהול מדידות מדעיות לפשט וסטנדרטיזציה על ידי שימוש במערכת אוניברסלית. אחד מהסיבות העיקריות שמערכת ה-SI משמשת ברחבי העולם היא הדיוק והדיוק במדידה שלה. אפשר למדוד כמויות הקטנות ביותר והגדולות ביותר בדיוק בעזרת יחידות הבסיס והקידמות שלהן. יחידת הבסיס לאורך במערכת ה-SI היא המטר, המוגדר כמרחק שבו תאורה מסתובבת בשואה במהלך מסגרת זמן מסוימת. באמצעות המערכת של הקידומות ניתן למצוא מידות אחרות כמו סנטימטר, קילומטר ומילימטר. יחידת הבסיס למסה במערכת ה-SI היא הקילוגרם, המוגדר ככמות המסה של מערכת אובייקטים בסיס בשם המצומצם "המחזור הבינלאומי של הקילוגרם". ניתן למצוא מדידות מסה אחרות כמו גרם ומיליגרם בעזרת המערכת של הקידומים. יחידת הבסיס לזמן במערכת ה-SI היא השנייה, המוגדרת כמשך 9,192,631,770 מחזורי הקרניות המשויכות למעבר מבין רמות האנרגיה הקשורות לאטום ציזיום-133 מסוים. משניות ניתן למצוא מדידות זמן אחרות כמו דקה ושעה בעזרת המערכת של הקידומים. בנוסף ליחידות אלה, הוגדרו עוד ארבעה יחידות כיחידות היסוד של מדידה. אלה הם האמפר, קלווין, מול וקאנדלה.</div>

מערכת היחידות הבינלאומית, הידועה בשם מערכת SI, היא מערכת מדידה מקובלת אוניברסלית המוכרת ונמצאת בשימוש ברחבי העולם. מערכת SI היא ...

Education

JoVE Core

Mechanical Engineering

הנדסת מכונות

Unit 1

יחידה 1

An Introduction to Statics

מבוא לסטטיקה

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

si units and metric prefixes

SI units and metric prefixes provide a standard way to measure size, mass, and time. The International System of Units, or SI system, is used worldwide because it gives scientists a common language for measurement. Its values do not change with location, which helps keep results consistent.

The SI system is built on three base units: meter, kilogram, and second. These are the core units for length, mass, and time. The kilogram is the only base unit that already includes a prefix.

Prefixes make it easy to express very large or very small values. Milli, micro, and nano represent smaller quantities. Kilo, mega, and giga represent larger quantities. SI prefixes are based on powers of ten, and the base unit has no prefix.

Several rules apply when writing SI units. Dots are used to separate units in composite units. A prefix should not appear in the denominator, only in the numerator. If a unit with a prefix is raised to a power, the power applies to both the prefix and the unit. The final answer should use just one prefix. Unlike the metric system, SI does not use deca or centi.

SI units help simplify and standardize scientific measurements. They also improve accuracy and precision, even for very small or very large quantities. The meter is defined as the distance light travels in a vacuum during a specific time frame. Other length units, such as centimeter, kilometer, and millimeter, come from the meter.

The kilogram is the SI base unit of mass. It was defined as the mass of a set of foundational objects called the International Prototype of the Kilogram. Grams and milligrams are derived from the kilogram. The second is the SI base unit of time and is defined by 9,192,631,770 cycles of radiation from a specific transition in cesium-133. Minutes and hours can be derived from the second. Four more fundamental units are also part of SI: ampere, Kelvin, mole, and candela.

SI Units and Metric Prefixes

an introduction to mechanics

Mechanics in Physics and Engineering

Mechanics is a key branch of physics that explains how objects stay at rest or move when forces act on them. It also has major uses in engineering and science. The topic helps students understand everyday motion, machine behavior, and the way many systems work. The recorded history of mechanics begins with Aristotle, who lived from 384 to 322 BC. He linked mechanics with physical theory and looked for a broad universal explanation. Later, Newton defined mechanics as the study of objects at...

basic concept

Fundamental Quantities in Engineering Mechanics

Engineering mechanics begins with four basic quantities: length, time, mass, and force. These ideas help describe how objects move and how they respond to loads. They also support many other engineering fields. Length measures the distance traveled by an object. Engineers describe this distance with coordinates relative to a reference point. Length is also useful for showing the geometry of physical systems. Time measures the succession of an event. A bus traveling from city X to city Y is a...

newton's law of motion

Newton's Laws and Everyday Motion

Newton's laws explain everyday motion and the forces that change it. These three laws describe why objects move, stay still, or speed up. They also show how force and mass affect motion. Newton's first law is the law of inertia. It says an object at rest stays at rest, and an object in motion keeps moving at a constant speed and direction unless an external force acts on it. A sliding box that slows down on its own is a good example. In that case, friction is the net external force that works...

newton's law of gravitational attraction

Gravity Between Masses and Distance

Newton’s law of gravitational attraction describes how gravity acts between two objects. Sir Isaac Newton built this law from empirical evidence and inductive reasoning. He published it in Philosophiae Naturalis Principia Mathematica, or the Principia, on July 5, 1687. The law says that the gravitational force between any two objects depends on their masses and their distance apart. The force is proportional to mass and inversely proportional to the square of the distance between the objects.

units of measurement

SI and Customary Measurement Systems

Mechanical engineering depends on units of measurement for precise and accurate calculations. These units give engineers a standard way to express and compare physical quantities. They are essential when designing and analyzing machines and mechanical systems. Many historical measurement systems have been used over time. Examples include the Babylonian system, the Roman system, the Egyptian system, the Olympian system, the British system, and the Indus Valley system. Today, the International...

international system of units

SI units and metric prefixes provide a standard way to measure size, mass, and time. The International System of Units, or SI system, is used worldwide because it gives scientists a common language for measurement. Its values do not change with location, which helps keep results consistent. The SI system is built on three base units: meter, kilogram, and second. These are the core units for length, mass, and time. The kilogram is the only base unit that already includes a prefix. Prefixes...

numerical calculations

Engineering Notation and Significant Figures

Numerical calculations in engineering depend on clear values, correct units, and careful rounding. Presenting the answer is an important part of engineering practice, so numerically accurate results are preferred. Handheld calculators and computers are often used because they help produce accurate answers. Problems can be solved in several ways. Solving algebraic symbols by hand is common, and the graphical method is often preferred in some cases. Computers are especially useful when many...

accuracy, limits, and approximation

Accuracy and Approximation in Calculations

Accuracy and approximation are important in calculations, especially in engineering. Accuracy means how close a measured value is to the true or actual value. Repeated measurements are often used in engineering mechanics to help make results more precise and accurate. The accuracy of a solution depends on empirical data and the results from different calculations or measurements. A cylindrical container filled with liquid is a simple example. Its volume can be found from the measured...

dimensional analysis

Using Dimensions to Check Physics Equations

Dimensional analysis is a useful way to check physics and engineering equations. It works by writing physical quantities in terms of basic dimensions such as mass, length, and time. Quantities like velocity, acceleration, and force are derived from these basic dimensions. This method helps compare measurements even when the units are different. It also checks whether an equation is dimensionally homogeneous. That means the powers of the fundamental dimensions must match on both sides of the...

problem solving in statics

Statics Problem-Solving Steps for Beams

Statics problem-solving uses a step-by-step method to analyze bodies in equilibrium, especially beams. It is an important part of physics and engineering because the goal is to find practical and accurate answers for real situations. The process usually starts with a physical situation and then turns it into a mathematical model. That model often needs approximations and assumptions. Very small distances can be ignored when they are much smaller than the main dimensions, such as beam width...

key terms and concepts

Learn how SI units use meters, kilograms, seconds, and metric prefixes to measure length, mass, and time with accuracy and consistency.

SI Units and Metric Prefixes | JoVE K12

JoVE Core Mechanical Engineering offers concise, easy-to-understand animated videos covering key topics such as equilibrium, forces, truss analysis, and structural mechanics. Explore their real-world applications, and witness these concepts in action through scientist-led experiments.

mechanical engineering

Physics

PHYS.1

PHYS.1.E

Chemistry and Physics

IPC.1

IPC.1.E

The Scientific Method

The scientific method is a detailed, empirical problem-solving process used by biologists and other scientists. This iterative approach involves ...

Inductive Reasoning

Inductive reasoning is a form of logical thinking that uses related observations to arrive at a general conclusion. It is uncertain and operates in ...

Deductive Reasoning

Deductive reasoning, or deduction, is the type of logic used in hypothesis-based science. In deductive reasoning, the pattern of thinking moves in the ...

Correlation and Causation

Correlation and CausationStatistical tests can calculate whether there is a relationship, or correlation, between independent and dependent variables. A ...

Ask questions and define problems related to specialized topics of study based on observations or information from text, phenomena, models, or investigations;

112.51.c.1.A.

Scientific Method

The scientific method is used to solve problems and explain phenomena. The development of the scientific method coincided with changes in philosophy ...

Demonstrating the Scientific Method with Tree Branches
ExpandObtain branches containing a few dozen typical leaves from five different local tree species. ...

Observation and Background Research
ExpandNOTE: The first two steps in the scientific process involve studying and observing natural phenomena of ...

Problem-Solving

A problem-solving strategy is a plan of action used to find a solution. It involves trial and error, algorithms, heuristics, and insights. Effective ...

Problem Definition

Problem definition is the initial and the most essential step in research.
The researcher identifies and explains the specific issue or gap to be ...

Apply science practices related to specialized topics of study to plan and conduct investigations or use engineering practices to design solutions to problems;

112.51.c.1.B.

Proper Personal Protective Equipment

Robert M. Rioux &#38; William A Elliott, Pennsylvania State University, University Park, PA
Hazards are many and varied in the laboratory, but the right ...

Emergency Eyewash and Shower Stations

Robert M. Rioux, Pennsylvania State University, University Park, PA
The Occupational Safety and Health Administration (OSHA) mandates that an emergency ...

Electrical Safety

Robert M. Rioux &amp; Suprita Jharimune, Pennsylvania State University, University Park, PA
Among the many hazards present in the laboratory, electrical ...

Working with Centrifuges

Source: Robert M. Rioux &amp; Suprita Jharimune, Pennsylvania State University, University Park, PA
Earth's gravitational force is capable of separating ...

Working with Hot and Cold Sources

Source: Robert M. Rioux &amp; Suprita Jharimune, Pennsylvania State University, University Park, PA
Working with extreme temperatures, both high and low, ...

guidelines-in-case-of-a-laboratory-emergency

Guidelines in Case of a Laboratory Emergency

Robert M. Rioux &amp; Zhifeng Chen, Pennsylvania State University, University Park, PA
The most common laboratory emergencies include chemical spills, ...

chemical-storage-categories-hazards-and-compatibilities

Chemical Storage: Categories, Hazards And Compatibilities

Source: Robert M. Rioux &amp; Taslima A. Zaman, Pennsylvania State University, University Park, PA
While the use of various chemicals in experimental ...

Safe Handling of Mineral Acids

Source: Robert M. Rioux &#38; Taslima A. Zaman, Pennsylvania State University, University Park, PA
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Handling Chemical Spills

Source: Robert M. Rioux &#38; Taslima Zaman, Pennsylvania State University, University Park, PA
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Proper Use of Autoclaves

Robert M. Rioux &amp; Zhifeng Chen, Pennsylvania State University, University Park, PA
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Fume Hoods and Laminar Flow Cabinets

Robert M. Rioux &amp; William A. Elliott, Pennsylvania State University, University Park, PA
Fume hoods and laminar flow cabinets are engineering controls ...

Decontamination for Laboratory Biosafety

Robert M. Rioux and Zhifeng Chen, Pennsylvania State University, University Park, PA
Decontamination is essential for laboratory biosafety, as the ...

Proper Waste Disposal

Robert M. Rioux and Taslima A. Zaman, Pennsylvania State University, Pennsylvania, PA

Users are responsible for the proper disposal of the waste ...

Use appropriate safety equipment and practices during laboratory, classroom, and field investigations as outlined in Texas Education Agency-approved safety standards;

112.51.c.1.C.

Common Lab Glassware and Uses

Source: Laboratory of Dr. Neal Abrams &#8212; SUNY College of Environmental Science and Forestry
Glassware is a regular appearance in the professional ...

Lab Techniques

Measurement Accuracy
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Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Preparation of LaboratoryExpand
	Here we show the laboratory preparation for 10 students ...

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Determining the Density of an EggExpand
	Density is a measure of how compact a substance or ...

Proper Lab Notebook Keeping

Organic Lab Notebook Keeping
Record keeping is a vital skill in science and organic chemistry labs. Without proper notes, descriptions, quantities, or ...

Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA

	Preparation of the LaboratoryExpand
	Here, we show the laboratory preparation ...

Source: Lara Al Hariri and Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA

	Nitration of Methyl BenzoateExpand
	From this lab onward, ...

Use tools appropriate to the specialized topic of study;

112.51.c.1.D.

SI Units: 2019 Redefinition

Measurement is integral to analytical chemistry. Each record comprises a number &#8211; denoting the magnitude&#160; &#8211; and the unit &#8211; a ...

The International System of Units, known as the SI system, is a universally accepted measurement system recognized and used worldwide. The SI system is ...

Measurement: Standard Units

Every measurement provides three kinds of information: the size or magnitude of the measurement (a number), a standard of comparison for the measurement ...

Measurement: Derived Units

The International System of Units or SI system, by international agreement, has fixed measurement units for seven fundamental properties: length, mass, ...

Collect quantitative data using the International System of Units (SI) or qualitative data as evidence as appropriate to the specialized topic of study;

Review and Preview

Data are individual items of information obtained from a population or sample. Data may be classified as qualitative (categorical), quantitative ...

What is a Frequency Distribution

A frequency is the number of times a value of the data occurs. The sum of all the frequency values represents the total number of students included in the ...

Cumulative Frequency Distribution

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Ogive Graph

An ogive graph is sometimes called a cumulative frequency polygon. It is one type of frequency polygon that shows cumulative frequency. In other words, ...

Histogram

The histogram is a graphical representation in the x-y form of data distribution in a data set. The horizontal x-axis is labeled with what the data ...

Relative Frequency Histogram

The relative frequency depicts the proportion of data points that have each value. The frequency tells the number of data points that have each value. ...

Scatter Plot

The most common and easiest way to display the relationship between two variables, x and y, is a scatter plot. A scatter plot shows the direction of a ...

Time-Series Graph

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Bar Graph

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Multiple Bar Graph

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Pareto Chart

A Pareto chart is a bar graph or a combination of both line and bar graphs. The bar lengths represent the individual values or the frequency, while the ...

Pie Chart

A pie chart (or a pie graph) is a circular graphical chart or a pictorial representation of categorical data. It is divided into slices of pie each ...

Organize quantitative or qualitative data using representations appropriate to the specialized topic of study such as scatter plots, line graphs, bar graphs, charts, data tables, diagrams, scientific drawings, and student-prepared models;

112.51.c.1.F.

Modeling and Similitude

A scaled model of a dam is tested in a controlled environment to observe how it will manage water flow, turbulence, and pressure.
This setup predicts the ...

Typical Model Studies

Typical model studies analyze scaled-down systems to predict fluid behavior, focusing on interactions with free surfaces and flow around immersed bodies.
...

design-example-creating-a-hydraulic-model-of-a-dam-spillway

Design Example: Creating a Hydraulic Model of a Dam Spillway

A hydraulic model of a dam spillway is often created by scaling down the design, typically to a 1:15 ratio, to replicate key flow characteristics such as ...

Models, Theories, and Laws

Scientists frequently use models to help them comprehend a specific collection of phenomena. In physics, a model is a condensed version of a physical ...

/files/media/science-education/science-education-thumbs/14686.jpg

Concepts and Prototypes

The human nervous system translates sensory stimuli into neural impulses, which the brain processes into information as thoughts and memories, forming ...

Molecular Models

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Develop and use models to represent phenomena, systems, processes, or solutions to problems as appropriate to the specialized topic of study; and

112.51.c.1.G.

Scientific Laws and Theories

Scientific Laws

In science, a law is defined as a concise, verbal or mathematical, statement that summarizes a vast number of experimental observations. ...

Distinguish among scientific hypotheses, theories, and laws as appropriate to the specialized topic of study.

112.51.c.1.H.

Identify advantages and limitations of models such as their size, scale, properties, and materials as appropriate to the specialized topic of study;

112.51.c.2.A.

Introduction to Statistics

The science of statistics involves collecting, analyzing, interpreting, and presenting data. The method of collecting, organizing, and summarizing data is ...

Statistical Analysis: Overview

An analysis is usually conducted by replicated sampling or repeated measurements on the same sample. This leads to scattered results rather than a single ...

systematic-error-methodological-and-sampling-errors

Systematic Error: Methodological and Sampling Errors

Systematic errors, depending on their source, are of four types &#8211; sampling, instrumental, method, and personal errors.
Sampling errors occur due to ...

Random Error

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types-of-errors-detection-and-minimization

Types of Errors: Detection and Minimization

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Realism in Experimentation

Source: Laboratories of Gary Lewandowski, Dave Strohmetz, and Natalie Ciarocco&#8212;Monmouth University

In an ideal world researchers would conduct ...

Bias

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Ethics in Research

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Analyze data appropriate to the specialized topic of study by identifying significant statistical features, patterns, sources of error, and limitations;

112.51.c.2.B.

Scientific and engineering practices. The student, for at least 40% of instructional time, asks questions, identifies problems, and plans and safely conducts classroom, laboratory, and field investigations to explain phenomena or design solutions using appropriate tools and models. The student is expected to:

SI Units and Metric Prefixes

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