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8/12/2019 Physical Quantities, Units and Dimensions
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Physical quantities
1. A physical quantity is a quantity that can be measured, i.e. speed, length, etc.
2. A non-physical quantity is a quantity that cannot be measubeauty, loyalty, feelings...
3. A physical quantity consists of a numerical magnitude and
4. Physical quantities are classified into base quantities and dquantities.
Mass of a book = 2000 g
(physical quantity) (numerical magnitude) (unit)
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Base quantity Unit Symbol
Length Metre MMass Kilogram kgTime Second sTemperature Kelvin KCurrent Ampere AAmount ofsubstance
Mole molLuminosity Candela cd
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Prefix Symbol Multiplication factor
Yotta Y 1 x 1024
Zetta Z 1 x 1021
Exa E 1 x 1018
Peta P 1 x 1015
Tera T 1 x 1012
Giga G 1 x 109
Mega M 1 x 106
Kilo k 1 x 103
Hecto h 1 x 102
Deca da 1 x 101
Deci d 1 x 10-1
Centi c 1 x 10-2
Milli m 1 x 10-3
Micro 1 x 10-6
Nano n 1 x 10-9
Pico p 1 x 10-12
Femto f 1 x 10-15
Atto a 1 x 10-18
Zepto z 1 x 10-21
Yocto y 1 x 10-24
Young Zookeepe
That Giant Man
david cute mous
father and zomb
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1. If the mass of a wooden block is m kg and its temperature heat content in joules (J) is given by the formula, = c is the specific heat capacity. What is the unit of c?
Solution:, =
=
Derived unit of c =
=
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2. Gravitational force is given by =
where dan ar
masses of two objects whereas R is the separation between the twFind the derived units of G, the universal gravitational constant.
Solution:
, =
=G
=
Derived unit of G =
G =
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1.4 Unit consistency & conversions1) 0.03 m = _____ cm
2) 2 109s = ________ ns
3) 7200 = ____________
n
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4) 123 = ___________
5) 2.16 = ________
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a) 22 has two significant figures
22.3 has three significant figures.
b) With zeroes, the situation is more complicated:i) Zeroes placed before other figures are not significant; 0.0
two significant figures.
ii) Zeroes placed between other figures are always significant;has four significant figures.
iii) Zeroes placed after other figures but behind a decimal poisignificant; 7.90 has three significant figures.
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c) 8200 has how many significant figures?
Normally is 2.
But better if you can write as below:
(i)8.200 103has four significant figures
(ii) 8.20 103has three significant figures
(iii) 8.2 103has two significant figures
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1. How many significant figures does each of the following nuhave?
a) 1230 b) 0.012 c) 0.0120 d) 12.30 e) 1.23
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