Uncertainties, Prefixes and Rounding Flashcards
What does the prefix G stand for?
G stands for giga
giga = x 109
What does the prefix µ stand for?
µ stands for micro
micro = x 10-6
Round off this number to 3 significant figures.
3.14159
3.14159 rounded off to 3 significant figures is
3.14
Round off this number to 3 significant figures.
6.22789
6.22789 rounded off to 3 significant figures is
6.23
Round off this number to 3 significant figures.
1,526.33
1,526.33 rounded off to 3 significant figures is
1,530
(the ‘2’ has been rounded up to 3)
What does the prefix n stand for?
n stands for nano
nano = x 10-9
Round off this number to 3 significant figures.
0.0025668
0.0025668 rounded off to 3 significant figures is
0.00257
What does the prefix k stand for?
k stands for kilo
kilo = x 103
What does the prefix M stand for?
M stands for mega
mega = x 106
What does the prefix m stand for?
m stands for milli
milli = x 10-3
Equation given on formula sheet
Explain what is meant by a random uncertainty, giving an example.
Random uncertainties are caused by random variations in experimental conditions e.g. random variations in background light levels due to changes in cloud cover.
Example
A length of card was measured by six people. The following
measurements were obtained: 21cm, 24cm, 22cm, 26cm, 25cm, 22cm.
Calculate the mean value with its random uncertainty.
Mean length = (21 + 24 + 22 + 26 + 25 + 22)/6
= 23.33 cm
Random Uncertainty = (highest value - lowest value)/number of measurements
= (26-21)/6
= 0.83 cm
= 0.8 cm to 1 sig fig and round mean to same decimal places
length = 23.3 ± 0.8 cm
What type of uncertainty is revealed by repeated measurement?
Random uncertainties would be revealed by variation in the measured values.
Explain what is meant by a systematic uncertainty, giving an example.
A systematic uncertainty is caused by incorrect use of equipment or faulty equipment that results in all readings being too high or low by a fixed amount e.g. not zeroing scales before using them.