The presentation is meant for senior secondary or A-Level physics students

1. Rationale and features of quantified observations
~Lalit Inshore, The Plenum School, HP

2. Rationale
 Scientific development happens through use of
scientific method that has the centrality of things
 Observations
 Measurements ( Precision & Accuracy important,
expressed in SI units)
 Collection of data / evidences
 Analysis of data
 Finding results and developing or refining theories

3. Flow chart of scientific method
Reject, accept or modify theory
Test or verify theory
Analyse and develop theory
Make and record measured or quantified observations

4. Concept of physical quantity

5. Base quantities and their SI units
Base or fundamental
quantity
Base or SI unit Symbol
MASS kilogram kg
LENGTH metre m
TIME second s
ELECTRIC CURRENT ampere / amp A
TEMPERATURE kelvin K
AMOUNT OF
SUBSTANCE
mol mol
LUMINOUS INTENSITY candela cd

6. Multiples (larger) and sub-multiples (smaller) or
multiplying factors of base units -1
 Expressed with prefixes to the base unit for scientific
communication
 Larger units
 Tera-T- 10 raised power 12
 Giga-G- 10 raised power 9
 Mega-M- 10 raised power 6
 Kilo-k- 10 raised power 3

7. Smaller multiples or multiplying
factors - 2
 Prefixes
 Deci-d- 10 raised power -1
 Centi-c- 10 raised power -2
 Milli-m- 10 raised power -3
 Micro – mu - 10 raised power -6
 Nano – n- 10 raised power -9
 Pico – p - 10 raised power -12

8. Significant figure
 The single digit with a multiplier prefix is ‘one significant
figure’
 Some values with one significant figure
 Radius of the Earth = 2 X 10 raised power 11 metre
 Wavelength of light = 5 X 10 raised power -7 metre
 Diameter of an atom = 3 X 10 raised power -10 metre
 Diameter of an atom = 6 X 10 raised power -15 metre
 Mass of the Sun = 2 X 10 raised power 30 kg
 Mass of hydrogen atom = 2 X 10 raised power -27 kg
 Mass of an electron = 9 X 10 raised power -31 kg
 Revolution time of the Earth = 3 X 10 raised power 7 s
 Time for light to travel 1 m = 3 X 10 raised power -9 s
 Time between heartbeats = 1 X 10 raised power 0 or 1 s

9. Order of magnitude
 Power of ten to which a number or quantity is raised for
approximation or for comparison
 Order of magnitude gives an estimation or approximation
of the value of a physical quantity
 For example
 Value of g is 9.81 metre per second square
 Approximate or rounded up value of g is 10 metre per second
square or 10 raised power 1
 Order of magnitude of 9 is one
 Another example
 The ratio of mass of whale to mouse is about is 10 raised
power 4 or it is ‘4 orders of magnitude’