Grade 12 Physics U
Lesson Summary #1
Key ideas #1
Physics studies fundamental questions about two entities.
What are these two entities?
Matter: anything that has mass
Energy:anything capable of doing work on matter by using a force to
move matter
Key Ideas #2
Physics deals with measured quantities.
Physicists use measuring instruments like rulers, clocks, and balances to assign a number value to physics “quantities”.
Physicists classify measured quantities into two major categories according to whether or not a quantity may have a direction or not. What are these two physics quantity types?
Vectors and Scalars
Key Ideas #3
Comparing Vectors and Scalars
Scalars
Size or magnitude
No direction
Temperature, distance, mass, speed, volume, area, energy and work
T = -7.0 C
Two parts: number and unit
Vectors
Size or magnitude
Has direction as well
Position, displacement, velocity, acceleration, force, magnetic field
v = 120 km/h [N30E]
Three parts: number, unit and direction
Key Ideas #4
Système Internationale or SI
A scientific measuring system with seven base or fundamental quantities
Each of the base or fundamental quantities has an associated base or fundamental unit
All other measurable quantities and units are combinations (+ - X / ) of the seven base quantities and are called derived quantities and units.
Page #2
The Seven Basic SI units
Fundamental QuantityLength
Mass
Time
Current
Temperature
Amount
Luminous intensity / Fundamental Unit
meter (m)
kilogram (kg)
second (s)
Ampere (A)
Degrees Kelvin (K)
mole (mol)
candela (cd)
Key Ideas #5
Short form for SI
An acronym for the SI metric system just discussed is given by the first letters in the SI base units of length, mass and time
meter kilogram second
Sometimes SI metric is referred to as the mks system, but there are other measurement systems with different base or fundamental quantities
Key Ideas #6
Other Measurement Systems
British Engineering System
fps or foot-pound-second system
used in Britain and in the U.S. in industry with derived units such as the gallon, slug, horsepower
Cgs System
centimeter-gram-second metric system
used in chemical engineering
☺Review question!!
In the SI or mks system, which of the following is not a derived quantity?
A.weight
B.density
C.mass
Answer: C
Density = mass/volume =kg/m3
Weight = force X acceleration = kg m/s2
page #3
Key Ideas #7
SI Prefixes
Small to Large10-24 = yocto (y)10-3 = milli (m)
10-21 = zepto (z)10-2 = centi (c)
10-18 = atto (a)10-1 = deci (d)
10-15 = femto (f)101 = deka (da)
10-12 = pico (p)103 = kilo (k)
10-9 = nano (n)106 = mega (M)
10-6 = micro (μ) 109 = giga (G) / Large to Very Large
1012 = tera (T)
1015 = peta (P)
1018 = exa (E)
1021= zetta (Z)
1024= yotta (Y)
Key Ideas #8
Writing Large or Small Quantities
Example:
The wavelength of red light is very small. It can bewritten with all the zero placeholders in expanded form like this:
λ = 0.000000631215 m (expanded form)
too many digits for most calculators
Scientific Notation
number equal or bigger than one but less than ten X power of ten
sometimes called standard form
λ = 0.000000631215 m (expanded form)
How can we write this wavelength in scientific notation?
λ = 6.31215 X ______?
= 6.31215 X 10-7 m
Enter in calculator as 6.31215 EXP (or E or EE) -7
Prefix Form
Number expressed as ones, tens or hundreds times a prefix in front of a unit name.
Example:
λ = 6.31215 X 10-7 m
Change the power of ten to the closest power of ten equal or less than the power of ten in scientific notation and associated with a SI prefix
λ = 631.215 X 10-9 m
λ = 631.215 X nm
page #4
☺Review!!
Convert the following expanded form physics quantities to standard and prefix form:
Electron charge
#1q = -0.000 000 000 000 000 000 1602 C
= -1.602 X 10-19 C or -160.2 zC
Mass of moon
#2m = 7360 000 000 000 000 000 000 0 kg
= 7.36 X 1022 kg or 73.6 Zg