Topic 1: Quantities and Measurements Flashcards
(23 cards)
What is a physical quantity
A physical quantity is a property of a material or system that can be quantified by measurement. Has a numerical magnitude and unit.
What statement to write when solving for unit of a quantity
Let [ ] denote ‘unit of’
Tera(T) is what power
10 ^12
Pico(p) is what power
10 ^ -12
m3 to cm3
x100 ^3
km/h to m/s
divide by 3.6
kg/m3 to g/cm3
divide by 1000
Estimate give to what sf
1sf
Estimate separation b/w two atoms in a solid
10 ^ -10m
Estimate radius of nucleus
10 ^ -15m
What is an error
An error is the difference between the measured value and the ‘true value’
What is random error
Random error is an error which causes measurements to be sometimes larger than the true value and sometimes smaller than the true value
How to reduce random error
- repeating same exp to obtain an average value
- draw a graph to obtain the line or curve of best fit
Example of random error
- experimental conditions
- non-constancy of experimental specimen
- error due to humans
What is systematic error
Systematic error is an error which causes measurements to be either, always larger than the true value or always smaller than the true value
(same magnitude and same sign)
Examples of systematic error
- zero error
- incorrectly calibrated instrument
- using the wrong constant
- wrong experiment procudure
What is precision
Precision refers to the degree of agreement of repeated measurements of the same quantity (spread/ scatter)
what is accuracy
degree of agreement b/w the result of measurements and the true value of the quantity (compared to true value)
absolute uncertainty of scale reading
1/2 smallest division
absolute uncertainty of measurement
smallest division
absolute uncertainty rules
1sf
give in standard form
how to express fractional/ percentage uncertainty
1sf/ 2sf
decimal
change in velocity formula
final velocity - initial velocity
