Understanding SI Units and Measurements
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Questions and Answers

Convert 0.45 km to meters.

450 m

What is 300 cm in meters?

3 m

Convert 5 MW to watts.

5,000,000 W

How many grams are in 525 kg?

<p>525,000 g</p> Signup and view all the answers

Convert 9 GJ into joules.

<p>9,000,000,000 J</p> Signup and view all the answers

What is the factor for the prefix 'milli'?

<p>10^-3</p> Signup and view all the answers

Identify the factor for giga in SI units.

<p>10^9</p> Signup and view all the answers

Convert 0.000005 m to micrometers.

<p>5 μm</p> Signup and view all the answers

What are the standard base units used in the International System of Units (SI) for time, temperature, mass, and length?

<p>Second for time, Kelvin for temperature, kilogram for mass, and meter for length.</p> Signup and view all the answers

What is the derived unit of force in the International System of Units (SI)?

<p>Newton (N).</p> Signup and view all the answers

How is the length of 1000 meters expressed using standard prefixes?

<p>1 kilometer (1 km).</p> Signup and view all the answers

What is the symbol for the standard prefix 'giga' and its corresponding factor?

<p>Symbol: G; Factor: $10^9$ (1,000,000,000).</p> Signup and view all the answers

Convert one megajoule (MJ) to joules (J).

<p>1 MJ = $10^6$ J.</p> Signup and view all the answers

What is the SI base unit for mass and its symbol?

<p>The SI base unit for mass is kilogram, symbolized as 'kg'.</p> Signup and view all the answers

What is the meaning of the prefix 'milli' in terms of its factor and symbol?

<p>Factor: $10^{-3}$ (1/1000); Symbol: m.</p> Signup and view all the answers

In which country is mass commonly measured in stone, and what is the SI unit for mass?

<p>In the UK, mass is measured in stone, but the SI unit for mass is the kilogram.</p> Signup and view all the answers

What is the SI unit for pressure and its derived unit?

<p>Pascal (Pa).</p> Signup and view all the answers

What are the consequences of using incompatible measurement units, illustrated by the Hubble telescope example?

<p>Using incompatible measurement units caused the Hubble telescope's mirrors to not fit, leading to transmission of fuzzy pictures.</p> Signup and view all the answers

List three SI base units along with their corresponding base quantities.

<p>Length - meter (m), time - second (s), temperature - kelvin (K).</p> Signup and view all the answers

What is the value of one kilonewton (kN) in newtons (N)?

<p>1 kN = 1000 N.</p> Signup and view all the answers

Name the SI unit for temperature and its symbol.

<p>The SI unit for temperature is kelvin, symbolized as 'K'.</p> Signup and view all the answers

What is the significance of using the base 10 system in the International System of Units?

<p>Using the base 10 system simplifies calculations and conversions among different units.</p> Signup and view all the answers

What are the SI units for electric current and luminous intensity?

<p>The SI unit for electric current is ampere (A) and for luminous intensity is candela (cd).</p> Signup and view all the answers

How are units of measurement commonly converted using prefixes in the SI system?

<p>Units are converted using prefixes that denote factors of 10, like kilo- for thousand or centi- for one hundredth.</p> Signup and view all the answers

Calculate the area of a rectangle measuring 5 cm by 20 mm, providing the answer in both cm² and mm².

<p>10 cm² and 1000 mm².</p> Signup and view all the answers

What is the correct number of significant figures for the area calculated from measurements of 12.6 cm and 5.8 cm, and why?

<p>73 cm² (2 sf) because the least number of sig figs used is in 5.8 cm, which has 2 significant figures.</p> Signup and view all the answers

Charlie measures the speed of a cyclist and finds it to be 9.536784741 m/s. What is the speed rounded to the correct number of significant figures?

<p>9.54 m/s (3 sf) because 3.67 s has the least number of significant figures, which is 3.</p> Signup and view all the answers

In calculating the speed, how should one approach unit conversions when given distance in meters and time in seconds?

<p>Ensure that distance is in meters and time in seconds before calculating speed using the formula speed = distance/time.</p> Signup and view all the answers

If a rectangle measures 12.6 cm and 5.8 cm, how would you express the area in both cm² and m²?

<p>Area is 73 cm² and 0.0073 m².</p> Signup and view all the answers

Convert 250 mA to Amperes.

<p>0.25 A</p> Signup and view all the answers

Convert 0.5 kN to Newtons.

<p>500 N</p> Signup and view all the answers

Convert 750 μm to meters.

<p>0.00075 m</p> Signup and view all the answers

What is 50 kJ in Joules?

<p>50,000 J</p> Signup and view all the answers

Convert 50 MPa to Pascals.

<p>50,000,000 Pa</p> Signup and view all the answers

Convert 2 m to centimeters.

<p>200 cm</p> Signup and view all the answers

If a snail travels 80 mm in 60 seconds, what is its speed in meters per second?

<p>1.33 m/s</p> Signup and view all the answers

Flashcards

SI Units

A system of units used in science and commerce. It simplifies measurements by using base 10.

Meter

The standard unit for measuring length in the SI system.

Kilogram

The standard unit for measuring mass in the SI system.

Second

The standard unit for measuring time in the SI system.

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Kelvin

The standard unit for measuring temperature in the SI system. It is based on absolute zero.

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Ampere

The standard unit for measuring electric current in the SI system.

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Mole

The standard unit for measuring the amount of a substance in the SI system.

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Candela

The standard unit for measuring luminous intensity in the SI system. It is a measure of light power.

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Millimeter (mm)

A unit of length equal to 1/1000 of a meter.

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Centimeter (cm)

A unit of length equal to 1/100 of a meter.

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Kilometer (km)

A unit of length equal to 1000 meters.

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Micrometer (μm)

A unit of length equal to 1/1,000,000 of a meter.

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Converting Units With Prefixes

To convert from a unit with a prefix to a unit without a prefix, multiply the number by the factor the prefix represents.

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Converting Units Without Prefixes

To convert from a unit without a prefix to a unit with a prefix, divide the number by the factor the prefix represents.

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Unit Conversion

The process of changing a unit of measurement to another unit.

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Meter (m)

The standard unit of length in the metric system.

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What is the equivalent of 1 gram (g) in kilograms (kg)?

Represents a quantity of 0.001 kilograms (kg).

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What is the equivalent of 1 kilometer (km) in meters (m)?

Represents a quantity of 1000 meters (m).

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What is the equivalent of 1 meter (m) in millimeters (mm)?

Represents a quantity of 1000 millimeters (mm).

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What is the equivalent of 1 meter (m) in micro-meters (µm)?

Represents a quantity of 1,000,000 micro-meters (µm).

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What is the equivalent of 1 gram (g) in milligrams (mg)?

Represents a quantity of 1000 milligrams (mg).

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What is the equivalent of 1 liter (l) in milliliters (ml)?

Represents a quantity of 1000 milliliters (ml).

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What is the equivalent of 1 kilojoule (kJ) in joules (J)?

Represents a quantity of 1000 joules (J).

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What is the equivalent of 1 megapascal (MPa) in pascals (Pa)?

Represents a quantity of 1,000,000 pascals (Pa).

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What is SI?

The International System of Units (SI) is the standard system of measurement used globally. It consists of seven base units: meter (m) for length, kilogram (kg) for mass, second (s) for time, Kelvin (K) for temperature, ampere (A) for electric current, mole (mol) for amount of substance, and candela (cd) for luminous intensity.

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What are Derived Units?

Derived units are units derived from the seven base units of the SI system. They are formed by combinations of base units using mathematical operations like multiplication, division, and exponentiation.

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What is the SI unit of force?

Newton (N) is the SI unit of force. It is defined as the force required to accelerate a mass of one kilogram at a rate of one meter per second squared.

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What is the derived unit of Force?

The derived unit of force is kg m/s², which stands for kilogram meter per second squared. This represents the fundamental relation between force, mass, and acceleration (F=ma).

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What are standard prefixes?

Standard prefixes are used to modify units, making it easier to work with very small or large quantities. For example, 'kilo' represents 1000, so 1 kilometer (km) equals 1000 meters (m).

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What does MJ stand for?

Megajoule (MJ) is a unit of energy equal to one million joules (J).

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What does nm stand for?

Nanometer (nm) is a unit of length equal to one billionth of a meter (1/1 000 000 000 m).

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What does kW stand for?

Kilowatt (kW) is a unit of power equal to one thousand watts (W).

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Calculating Area with Different Units

The area of a rectangle is calculated by multiplying the length and width. To calculate the area in different units, make sure the units are consistent throughout the calculation. Use the conversion factor twice for square units.

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Significant Figures in Calculations

Significant figures are used to represent the precision of a measurement. The final answer should not have more significant figures than the least number of significant figures in the data used in the calculation.

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Calculating Speed

When calculating speed, divide the distance traveled by the time taken. Remember to use consistent units throughout the calculation.

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Rounding to Significant Figures

The final answer should be expressed with the same number of significant figures as the least precise measurement used in the calculation. Round up if necessary.

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Multiplication with Significant Figures

When multiplying measurements, the final answer should have the same number of significant figures as the measurement with the least number of significant figures.

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Study Notes

Learning Objectives

  • Correctly use significant figures
  • Identify SI units
  • Convert measurement units using prefixes

SI Units

  • Examples of time units: minutes, seconds, hours, days
  • Example of mass units: kilograms, stone, pounds
  • Examples of units that are NOT part of the SI system: ounces, gallons, Fahrenheit, miles, litres, pint, yards, inches, Celsius, feet

SI Units - Fixing the Problem

  • The International System of Units (SI) is based on the metric system and uses base 10
  • Widely used in science and commerce, replacing other systems like "imperial"
  • Developed in 1960

SI Base Units

Base Quantity Name Symbol
length meter m
mass kilogram kg
time second s
electric current ampere A
temperature Kelvin K
amount of substance mole mol
luminous intensity candela cd

Derived Units

  • The derived unit of force is Newton (N)
  • The SI unit of force is kg m/s² (kilogram meter per second squared)

Prefixes

  • Standard prefixes modify units to measure very small or very large quantities e.g. length of 1000 m is the same as 1 km
Factor Name Symbol
109 (1 000 000 000) giga G
106 (1 000 000) mega M
103 (1 000) kilo k
10-2 (1/100) centi c
10-3 (1/1000) milli m
10-6 (1/1 000 000) micro μ
10-9 (1/1 000 000 000) nano n

Converting Units

  • To convert from a unit with a prefix to a unit without a prefix, multiply by the factor associated with the prefix. Conversely, divide to remove a prefix.

Significant Figures

  • The final answer cannot have more significant figures than the measurement with the fewest significant figures used in the calculation
  • Unlike mathematics, you do not get the number of significant figures (sig figs) required for your final answer
  • Work out from the data and round off if necessary

Example: Significant Figures

  • If a rectangle is 12.6 cm long and 5.8cm wide, the final area to the correct number of significant figures is 73 cm2 (2sf, based on the least precise measurement of 5.8)

Example: Speed

  • If a snail travels 80 mm in 60 s, the speed is 1.3 mm/s, 0.13 cm/s, or 0.08 m/min

Example: Area Measurement

  • If a rectangle is 5 cm by 20 mm, its area is 10 cm2 or 1000 mm2

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Related Documents

F3 SI Units and Measurement PDF

Description

This quiz focuses on significant figures, SI units, and unit conversions. Learn to identify different measurement units and understand the importance of the International System of Units. Test your knowledge on both base and derived SI units.

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