Transcript What is a physical quantity?

Mathematics
Math in Physics
What is a physical quantity?
A physical quantity is any quantity that can be measured with a
certain mathematical precision.
Example: Force
What is a dimension?
The product or quotient of fundamental physical quantities, raised
to the appropriate powers, to form a derived physical quantity.
Example: mass x length / time2 (ML/T2)
What is a unit?
A precisely defined (standard) value of physical quantity against
which any measurements of that quantity can be compared.
Example: Newton = kilogram x meters / second2
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Mathematics
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Sytème International
2
temperature
Kelvin (K)
length
meters (m)
current
time
seconds (s)
amount of substance
Mole (mol)
mass
kilograms (kg)
luminous intensity
candela (cd)
Amperes (A)
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US Customary System
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temperature
Fahrenheit (F)
length
inches (in, ")
current
time
seconds (s)
amount of substance
Mole (mol)
mass
pounds (lb)
luminous intensity
candela (cd)
Amperes (A)
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Other units
length
Feet (ft, '), mile (m, mi), furlong, hand
time
minute (m, min), hour (hr), second (s), fortnight, while
energy
force
Joule (J)
Newton (N)
power
temperature
Watt (W)
Celsius (C)
pressure
Pascal (P)
magnetic field
Tesla (T), Gauss (G)
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Common conversion factors
length
1 in = 2.54 cm
time
60 s = 1 min, 60 min = 1 hr, 24 hours = 1 day, 365.25 days= 1 yr
force
1 N = 0.2248 lb
energy
1 J = 107 erg, 1 eV = 1.602x10-19 J
power
1 hp = 746 W
pressure
1 atm = 101.3 kPa
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magnetic field
1 T = 104 G
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How to convert units
24 hr 60 min 60 sec
1 day  1 day
1 day 1 hr 1 min
1 day  24  60  60 sec
1 day  86,400 sec
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Most commonly used prefixes for powers of 10
tera
giga
mega
kilo
centi
milli
micro
nano
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T
G
M
k
c
m
μ
n
1,000,000,000,000
1,000,000,000
1,000,000
1000
0.01
0.001
0.000001
0.000000001
1012
109
106
103
10-2
10-3
10-6
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Common physical quantities
Mass
Distance
Time
Speed / Velocity
Acceleration
Force
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What is scientific notation?
1,562,788.
0.0012789
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 1.562788x106
 1.2789x10-3
Mathematics
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Using scientific notation in calculators
When putting numbers in a calculator, it is best to
covert them to non-prefixed units first (e.g. 1mm 
1x10-3 m) and then convert back to the desired units
when the problem is complete.
When using a calculator, it is also better to put in the
full number (e.g. 1350x10-3 m instead of 1.35 m for 1350
mm). In this way you will avoid many of the “decimal
place errors” so common in this class.
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