mathematics math in physics 1 what is a physical quantity? a physical quantity is any quantity that...
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MathematicsMath in Physics
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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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Sytème International
lengthmeters (m)
timeseconds (s)
masskilograms (kg)
temperatureKelvin (K)
currentAmperes (A)
amount of substanceMole (mol)
luminous intensitycandela (cd)
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US Customary System
lengthinches (in, ")
timeseconds (s)
masspounds (lb)
temperatureFahrenheit (F)
currentAmperes (A)
amount of substanceMole (mol)
luminous intensitycandela (cd)
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Other unitslength
Feet (ft, '), mile (m, mi), furlong, hand
timeminute (m, min), hour (hr), second (s), fortnight, while
forceNewton (N)
temperatureCelsius (C)
energyJoule (J)
powerWatt (W)
pressurePascal (P)
magnetic fieldTesla (T), Gauss (G)
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Common conversion factors
length1 in = 2.54 cm
time60 s = 1 min, 60 min = 1 hr, 24 hours = 1 day, 365.25 days= 1 yr
force1 N = 0.2248 lb
energy1 J = 107 erg, 1 eV = 1.602x10-19 J
power1 hp = 746 W
pressure1 atm = 101.3 kPa
magnetic field1 T = 104 G
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How to convert units
day 1day 1
sec day 6060241
sec day 400,861
day 1
hr 24
hr 1
min 60
min 1
sec 60
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Most commonly used prefixes for powers of 10
tera T 1,000,000,000,000 1012
giga G 1,000,000,000 109
mega M 1,000,000 106
kilo k 1000 103
centi c 0.01 10-2
milli m 0.001 10-3
micro μ 0.000001 10-6
nano n 0.000000001 10-9
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Common physical quantities
MassDistanceTimeSpeed / VelocityAccelerationForce
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What is scientific notation?
1,562,788. 1.562788x106
0.0012789 1.2789x10-3
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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.