Measurements and errors Flashcards
What are the fundamental base units?
metre, m
second, s
kilogram, kg
kelvin, k
ampere, A
mole, mol
candella, cd
What are the units ranging from pico to tera?
pico 10 -12
nano 10 -9
micro 10 -6
milli 10 -3
centi 10 -2
deci 10 -1
deca 10 1
hecto 10 2
kilo 10 3
mega 10 6
giga 10 9
tera 10 12
What is the difference between accurate and precision?
accuracy is close to the true value very
precise results have little spread from the mean value
What is the difference between repeatability and reproduceability
repeatability is a measurement that when the original experiment is repeated, the results obtained are the same
reproducibility getting the same results by using different equpment
What is uncertainty and how do we measure it?
a interval in which we expect to find the true value
finest value / value obtained x100
What are the different errors?
measurement error is when the measured value is different from the true value
random error is caused by factors which vary from one experiment to the other
systematic errors are errors in the equipment, they are usually predictable and propotional to the true value
zero error is where the meter gives a non zero reading when the quantity is zero
What are some examples of systematic errors?
parallax - not looking parallel to the object being measured faulty equipment reaction time
How can we prevent systematic errors?
higher precision equipment higher precision students calibration repeat
How do we combine uncertainties?
when multiplying uncertainties we add the uncertainties together
when squaring we double the uncertainties
when powering the uncertainty, multiply the uncertainty by the power
How do you reduce parallax?
- look horizontal to measurement
- or use set square to measure the position of the lower end of the spring agianst the veritcal mm rule toreduce parallax
How do you convert from km2 to m2
x106
= (1x103)2
