Units/uncertainty Flashcards
Tera
10 to the 12
T
Giga
10 to the 9
G
Mega
10 to the 6
M
Kilo
10 to the 3
k
Milli
10 to the minus 3
m
Micro
10 to the minus 6
µ
Nano
10 to the minus 9
Pico
10 to the minus 12
p
Femto
10 to the minus 15
f
Standard units
s m kg A K (kelvin) mol
Thermodynamic temperature unit
Kelvin (K)
Light intensity unit
Candela (cd)
Amount of substance
mole (mol)
Homogenous
Using the base units of each side to show that both sides are equal so the equation works
Random error
Errors where the measurements vary from the true value by different amounts, cannot be avoided but are minimised by having more attempts
Systematic error
Where the measurements vary from the true value by the same amount each time
Accuracy
How close your answers are to the true value
Precision
A measure of how close your results are to the mean
Absolute uncertainty
Range/2 or the resolution if you only have 1 value
The interval that a value is said to lie in with a given level of confidence
Percentage uncertainty
Absolute uncertainty/value x 100
Combining uncertainties
For + or - add absolute uncertainties
For x or / add percentage uncertainties and convert back
For raising a quantity to a power multiply the percentage uncertainty by the power and convert back
For multiplying the answer by a value percentage uncertainty is the same or multiply absolute uncertainty by the factor
Error bars
Represent uncertainty on a graph
Draw one line horizontally for x variable and vertically for y from each point
e.g.
_
|
|—x—|
|
-
What to plot on a line graph
Points
Error bars
Line of best fit
Line of worst fit (steepest line that touches all y error bars)
Absolute uncertainty in gradient
Positive difference between the gradient of lines of best and worst fit
Percentage uncertainty in the gradient
(Absolute uncertainty/ gradient of line of best fit) x100
Weight
A force due to gravity, measured in Newtons
uses of g
The gravitational field strength, g = 9.81 Nkg-1
The acceleration due to gravity, g = 9.81 ms-2
Force on base units
kgms^-2
Anomaly definition
A data point that doesn’t follow the general trend
Volume of a sphere
4/3 π r^3
