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Physics - atoms and molecules in motion > SI units > Flashcards

SI units Flashcards

1
Q

What are SI units?
(Publication date, where used)

A

A metric system of measurement comprising seven base units, derived units and prefixes. These can be used to produce fractions or multiples of units by a factors of 10.
Published in 1960
Adopted throughout the world, except in the USA

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2
Q

What are the seven fundamental SI units?

A

Acronym SMMACKK:
Second (s)
Mole (mol)
Metre (m)
Ampere (A)
Candela (cd)
Kelvin (K)
Kilogram (kg)
All other units in the SI system can be derived from these seven base units

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3
Q

Second
(symbol, quantity of, description)

A

s
Time
The duration of a certain number of oscillations of a caesium-133 atom

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4
Q

Mole
(symbol, quantity of, description)

A

mol
Amount of substance
The amount of substance that contains the same number of particles as there are atoms in 0.012 (12g) of carbon-12

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5
Q

Metre
(symbol, quantity of, description)

A

m
Length or distance
Length travelled by light in a vacuum in 1/300,000,000 of a second

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6
Q

Ampere
(symbol, quantity of, description)

A

A
Electric current
The current in two parallel conductors of infinite length, placed 1m apart in a vacuum that would produce force of 2x10-7 N/m

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7
Q

Candela
(symbol, quantity of, description)

A

cd
Intensity of illumination
Luminous intensity of monochromatic light

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8
Q

Kelvin
(symbol, quantity of, description)

A

K
Thermodynamic temperature
1/273.16 of the thermodynamic triple point of water

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9
Q

Kilogram
(symbol, quantity of, description)

A

kg
Mass
The mass of the prototype kilogram held in Sevres, France. NB this is the only physical quantity within the base units. However there is debate about whether to change this as the prototype is slowly degrading

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10
Q

What is the base unit for time?

A

Second
=the duration of a certain number of oscillations of a caesium-133 atom

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11
Q

What is the base unit for amount of substance

A

Mole (mol)
=the amount of substance that contains the same number of particles as there are atoms in 0.012kg (12g) of carbon-12

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12
Q

What is the base unit for length or distance

A

Metre (m)
=length travelled by light in a vacuum in 1/300,000,000 of a second

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13
Q

What is the base unit for electric current

A

Ampere (A)
=the current in two parallel conductors of infinite length, placed 1m apart in a vacuum that would produce force of 2x10-7 N/m

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14
Q

What is the base unit for intensity of illumination

A

Candela (cd)
=Luminous intensity of monochromatic light

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15
Q

What is the base unit for temperature

A

Kelvin (K)
=1/273.16 of the thermodynamic triple point of water

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16
Q

What is the base unit for mass?

A

Kilogram (kg)
=the mass of the prototype kilogram held in Sevres, France

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17
Q

How do prefixes to SI units work?

A

Any SI unit can have a prefix which gives it a fraction or multiple of 10. When used it is still classified as an SI unit
e.g. a centimeter is 0.01 of a metre, and therefore STILL classified as an SI unit.
For example, although pascal is the SI unit for pressure, kilopascal is also classed as an SI unit as it uses the kilo-prefix
Note that while the base unit for mass is the kilogram, prefixes to mass work relative to a gram.

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18
Q

State the symbol and multiple of 10 of the following SI prefixes:
Pico
Nano
Micro
Milli
Centi
Deci

A

Pico (p): 10-12
Nano (n): 10-9
Micro (µ): 10-6
Milli (m): 10-3
Centi (c): 10-2
Deci (d): 10-1

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19
Q

State the symbol and multiple of 10 of the following SI prefixes:
Deca
Hecto
Kilo
Mega
Giga
Tera

A

Deca (da): 10^1
Hecto (h): 10^2
Kilo (k): 10^3
Mega (M): 10^6
Giga (G): 10^9
Tera (T): 10^12

20
Q

Area
(Derived unit of, symbol)

A

Square metre
m^2

21
Q

Volume
(Derived unit of, symbol)

A

Cubic metre
m^3

22
Q

Speed
(Derived unit of, symbol)

A

metres per second
m.s^-1

23
Q

Velocity
(Derived unit of, symbol)

A

metres per second, with direction
m.s^-1

24
Q

Acceleration
(Derived unit of, symbol)

A

metres per second squared
m.s^-2

25
Q

Current density
(Derived unit of, symbol)

A

Ampere per square metre
A.m^-2

26
Q

Hertz
(symbol, quantity of, equivalents, SI base unit)

A

Hz
Frequency
No equivalents
s^-1

27
Q

Newton
(symbol, quantity of, equivalents, SI base unit)

A

N
Force
No equivalents
kg.m.s^-2 aka kg x m/s2

Note: newtons are the product of mass (kg) multiplied with acceleration (metres per second per second squared)

28
Q

Pascal
(symbol, quantity of, equivalents, SI base unit)

A

Pa
Pressure, stress
N/m^2
kg.m^-1.s^-2 aka kg/m/s2

29
Q

Joule
(symbol, quantity of, equivalents, SI base unit)

A

J
Energy, work, heat
N⋅m, C⋅V, W⋅s
kg⋅m^2⋅s^-2 aka kg x m2/s2

30
Q

Watt
(symbol, quantity of, equivalents, SI base unit)

A

W
Power
J/s, V⋅A
kg⋅m^2⋅s^-3

31
Q

Coulomb
(symbol, quantity of, equivalents, SI base unit)

A

C
Electrical charge or quantity
No equivalents
s.A

32
Q

Volt
(symbol, quantity of, equivalents, SI base unit)

A

V
Voltage, electrical potential
W/A, J/C
kg⋅m^2⋅s^-3⋅A^-1

33
Q

Farad
(symbol, quantity of, equivalents, SI base unit)

A

F
Capacitance
C/V, s/Ω
kg^-1⋅m^-2⋅s^4⋅A^2

34
Q

Ohm
(symbol, quantity of, equivalents, SI base unit)

A

Ω
Resistance, impedance
V/A
kg⋅m^2⋅s^-3⋅A^-2 aka kg x m2/s3/A2

35
Q

Henry
(symbol, quantity of, equivalents, SI base unit)

A

H
Inductance
V.s/A
kg⋅m^2⋅s^-2⋅A^-2

36
Q

Weber
(symbol, quantity of, equivalents, SI base unit)

A

Wb
Magnetic flux
T.m^2
kg⋅m^2⋅s^-2⋅A^-1

37
Q

Tesla
(symbol, quantity of, equivalents, SI base unit)

A

T
magnetic flux density
Wb/m^2
kg⋅s^-2⋅A^-1

38
Q

Define one day in the SI system

A

Time is NOT in the SI system
1 day is 86,400 seconds i.e. 86.4 kiloseconds in the SI system

39
Q

Define Litre in the SI system

A

Litres (and derivatives e.g. ml) are NOT in the SI system
1L = 1000 cm^3

40
Q

Define degrees celsius in the SI system

A

Degrees celsius is NOT in the SI system
Convert degrees celsius to kelvin by adding 273.15
i.e. 1 degree celsius = 274.15K

41
Q

What is the conversion between atmosphere, bar kPa, mmHg and cmH20

A

1 atmosphere = 1.013 Bar = 101.3 kPa = 760mmHg = 1020 cmH20

42
Q

What is the conversion between kPa and mmHg?

A

1kPa = 7.6 mmHg

43
Q

What is the conversion between between cmH2O and mmHg?

A

10cmH2O = 7.6mmHg

44
Q

Define weight

A

Weight is force acting upon mass
i.e. people on the moon have less force i.e. gravity acting upon them so they weigh less, even though their mass is the same

45
Q

What is the conversion between celsius and Kelvin?

A

Kelvin = celsius - 273.15

46
Q

Do derived units always have to be expressed as base units?

A

No
Derived units can be expressed as base units, a combination of base and derived units, or two derived units.
The Pascal, for example, can be expressed as base units (kg/m-1/s-2) or a combination of base and derived units (N/m2).

Physics - atoms and molecules in motion (3 decks)

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