Lectures 1-7 Flashcards
SI units
Used to standardise quantities used to measure physical properties including time, lengths, depth, mass, time, and energy. SI units help us communicate in a consistent universal way.
Common SI units
Length metre m
Mass kilogram kg
Time second s
Electric current ampere A
Temperature kelvin K
Amount of substance mole mol
Luminous intensity candela cd
Derived quantities
combinations of SI units for example;
Speed = metre per second = m/s
Prefixes
Extremely large or extremely small numbers
Common prefixes
Giga G 10^9
Mega 10^6
Kilo 10^3
Centi 10^-2
Milli 10^-3
Micro 10^-6
Nano 10^-9
Scientific notation
expressing number to the power of 10
for example;
1,000 = 1x10^3
3,000 = 3 x10^3
40,000 = 4 x 10^4
Combining units with scientific notation
Every answer you give in physics needs units
The speed of light = 3.00 x 10^8 m/s
Significant figure
indicate the precision of a number/measurement
non-zero numbers
123 has 3 significant figures
zeros between non-zero numbers
1002 has 4 significant figures
leading zeros
0.00045 has 2 significant figures
trailing zeros (if there’s a decimal place then yes if no decimal place then no)
50.0 has 3 significant figures
500 has 1 significant figure
exact numbers
counted items such as “3 apples” has an infinite number of significant figures as it is not measured but counted
why significant figures are important
more precise measurements
12m is less accurate than 12.00m
Rule for multiplying/dividing
the answer should have the same amount of significant figures as the one with the SMALLEST significant figures.
3.2 x 4.56 =14.6
Rule for adding/subtracting
The answer should have the same amount of decimal places as the one with the SMALLEST amount of decimal places.
12.34 + 0.6 =12.9
uncertainties
every measurement has an uncertainty
usually expressed as +/-
shows the range of values within which the true values lie
5.6cm +/- 0.1cm means that the true value could be between 5.5cm or 5.7cm