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?

525,000 g Signup and view all the answers

Convert 9 GJ into joules.

9,000,000,000 J Signup and view all the answers

What is the factor for the prefix 'milli'?

10^-3 Signup and view all the answers

Identify the factor for giga in SI units.

10^9 Signup and view all the answers

Convert 0.000005 m to micrometers.

5 μm 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?

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

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

Newton (N). Signup and view all the answers

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

1 kilometer (1 km). Signup and view all the answers

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

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

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

1 MJ = $10^6$ J. Signup and view all the answers

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

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

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

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

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

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

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

Pascal (Pa). Signup and view all the answers

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

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

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

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

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

1 kN = 1000 N. Signup and view all the answers

Name the SI unit for temperature and its symbol.

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

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

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

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

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

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

Units are converted using prefixes that denote factors of 10, like kilo- for thousand or centi- for one hundredth. 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.

10 cm² and 1000 mm². 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?

73 cm² (2 sf) because the least number of sig figs used is in 5.8 cm, which has 2 significant figures. 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?

9.54 m/s (3 sf) because 3.67 s has the least number of significant figures, which is 3. 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?

Ensure that distance is in meters and time in seconds before calculating speed using the formula speed = distance/time. 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?

Area is 73 cm² and 0.0073 m². Signup and view all the answers

Convert 250 mA to Amperes.

0.25 A Signup and view all the answers

Convert 0.5 kN to Newtons.

500 N Signup and view all the answers

Convert 750 μm to meters.

0.00075 m Signup and view all the answers

What is 50 kJ in Joules?

50,000 J Signup and view all the answers

Convert 50 MPa to Pascals.

50,000,000 Pa Signup and view all the answers

Convert 2 m to centimeters.

200 cm Signup and view all the answers

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

1.33 m/s Signup and view all the answers

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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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.