Physical Quantities and units Flashcards

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1
Q

What is a physical quantity?

A

Physical quantities are those which can be measured, for example: length, mass, weight, speed, force, momentum, time etc. Every physical quantities has a numerical value and a unit.

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2
Q

What are base quantities?

A

Base Quantities are those quantities which require only one measurement. They are seven in number.

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3
Q

How many base Quantities are there?

A

The seven base quantities are:
Length-meter-m
Mass-Kilogram-Kg
Time-Second-S
Electrical current-Ampere-A
Temperature-Kelvin-K
Amount of Substance-Mole-mol
Luminous Intensity-Candela-cd

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4
Q

What are base units?

A

The units of the base quantities are known as base units.

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5
Q

What are derived quantities?

A

Physical quantities other than base quantities are called derived quantities, as they require more than one measurement.

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6
Q

What are derived units?

A

They can be derived from the relationship between the derived quantities and the base quantities.

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7
Q

What are the derived Quantities?

A

Area
Volume
Density
Velocity
Acceleration
Force
Energy/work
Kinetic Energy
Potential Energy
Power
Pressure
Charge
Frequency
Momentum
Electrical resistance
Voltage
Strain
Spring Constant
Potential Difference

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8
Q

What is the formula and derived units for area?

A

LxL=pier^2
Derived units=mxm=m^2

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9
Q

What is the formula and derived units for volume?

A

LxLxL=m^3
Derived units=m^3

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10
Q

What is the formula and derived units for density?

A

mass/volume
Derived Units:
mass=kg
volume=m3
hence density=kg m-3

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11
Q

What is the formula and derived units for velocity?

A

velocity=distance/time
Derived Units:
distance: m
time: s
hence velocity= m s-1

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12
Q

What is the formula and derived units for acceleration?

A

acceleration: a = Δv/Δt
Derived Units:
Velocity: m s-1
time: s
hence acceleration= m s-2

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13
Q

What is the formula and derived units for force?

A

Force: mass x acceleration
Derived Units:
mass=kg
acceleration= m s-2
hence force= kg m s-2

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14
Q

What is the formula and derived units for energy/word?

A

Energy/work: force x distance
Derived units:
force: kg m s-2
distance: m
Hence energy/work: kg m^2 s-2

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15
Q

What is the formula for kinetic energy?

A

1/2 mv^2
where m=mass
v=velocity

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16
Q

What is the formula for potential energy?

A

mgh
where m= mass
g=acceleration due to gravity=9.8 m s-2
h=height

17
Q

What is the formula and derived units for power?

A

power=energy/time
energy=kg m^2 s-2
time: s
hence power=kg m^2 s-3

18
Q

What is the formula and derived units for pressure?

A

pressure=force/area
force=kg ms-2
area=m^2
hence pressure: kg m-1 s-2

19
Q

What is the formula and derived units for charge?

A

charge: current x time
current= A
Time= s
hence charge= As

20
Q

What is the formula and derived units for frequency?

A

frequency=1/t
time=s
hence frequency=s-1

21
Q

What is the formula and derived units for electrical resistance?

A

electrical resistance= voltage/current
voltage: kg m2 s-3 A-1
current: A
hence electrical resistance: kg m2 s-3 A-2

22
Q

What is the formula and derived units for momentum?

A

momentum= mass x velocity
mass=kg
velocity=ms-1

23
Q

What is the formula and derived unit for voltage?

A

voltage= current x resistance
current= A
charge=As
hence voltage= A^2 s

(check)

24
Q

What is the formula and derived unit for specific heat capacity?

A

Specific heat capacity=

25
Q

What is the formula and derived unit for strain?

A

Strain=extension/length
extension=m
length=m
hence strain has no units.

26
Q

What is the formula and derived unit for young modulus?

A

Young Modulus=Stress/Strain
Stress= Kg m-1 s-2
strain=no units
Hence Young Modulus: Kg m-1 s-2

27
Q

What is the formula and derived units of spring constant?

A
28
Q

What is the formula and derived units of potential difference?

A

Potential difference= energy/charge
Energy=kg m^2 s-2
Charge=As
Hence potential difference= kg m^2 s-3

29
Q

What are prefixes?

A

Prefixes are multiples or submultiples of the base units.

30
Q

What are the four multiples?

A

Kilo- 10^3-K
Mega-10^6-M
Giga-10^9-G
Tera-10^12-T

31
Q

What are the four submultiples?

A

Milli-10^-3-m
Micro-10^-6- µ
Nano-10^-9-n
Pico-10^-12-p

32
Q

What is meant by homogeneity of equation?

A

An equation is said to be homogenous if the base units of every term in the equation are identical.

33
Q

What is the volume of a cylinder?

A

Volume of a cylinder: πr2h