Chapter 1 - Physical Quantities & Measurements Flashcards
Prefix and symbol for 1000000000
giga (G)
Prefix and symbol for 1000000
mega (M)
Prefix and symbol for 1000
kilo (k)
Prefix and symbol for 0.1
deci (d)
Prefix and symbol for 0.01
centi (c)
Prefix and symbol for 0.001
milli (m)
Prefix and symbol for 0.000001
micro (µ)
Prefix and symbol for 0.000000001
nano (n)
What is precision?
reproducibility
A measurement is precise if…
it is close to other values obtained by repeating the determination using the same procedure
What is accuracy?
correctness
A measurement is accurate if…
it is close to the true value.
Since the true value of a quantity can never be exactly known, an ________ value is commonly used as the test of ________
accepted
accuracy
What is an error?
- anything that causes a measurement to differ from the true value
or - the amount by which the measure value differs from the true value
A more precise instrument is one that can…
measure smaller intervals
the values given are likely to be closer together, hence it is more precise
What is a random error?
An error that occurs inconsistently each time a measurement is repeated
Random errors can be caused by…
- the inaccurate reading of the observer from a scale (e.g. parallel error, human judgement error)
- background disturbance (e.g. wind, background noise, vibration in the environment)
Random errors cause…
poor precision
Random errors can be reduced by…
averaging the results of repeated measurements
What is a systematic error?
An error that occurs inconsistently each time a measurement is repeated
Systematic errors can be caused by…
- the zero error of the instrument
- the instrument being incorrectly calibrated
Systematic errors can be detected by…
comparing with a calibration standard
Systematic errors cause…
poor accuracy
Systematic errors can be adjusted by…
applying a correction factor
Precision indicates…
the size of random errors in a set of measurements
how close the readings are to the average value
If an experiment has small random errors, it has ________ precision — the readings are close to the ________ value
high
average
Accuracy indicates…
the size of systematic errors in a set of measurements
how close the readings are to the true value
If an experiment has small systematic errors, it has ________ accuracy — the readings are close to the ________ value
high
true
The number of decimal places is determined by the ________ used
units
All non-zero digits are ________
always significant
Zeros between two other significant digits are ________
always significant
Trailing zeros (on the right) in a number containing a decimal point are ________
significant
Leading zeros (on the left) in a number containing a decimal point are ________
not significant
The significance of trailing zeros in a number not containing a decimal point can be ________
ambiguous
but in a question, consider 3500 as 4s.f.
There should be at least ______ sets of readings for a straight line graph
6
There should be at least ______ sets of readings for a curved graph
8
Precautions for checking horizontal and vertical alignments [3]
- Use a spirit level or a plumbline and a set-square to check whether the apparatus or set-up is horizontal or vertical
- Measure both ends from the top of the bench to judge whether the apparatus or setup is horizontal
- Make use of the edge of a door, blackboard, or a wall to judge whether the apparatus or set-up is horizontal or vertical
Precautions for experiments involving pendulums [3]
- The angle of oscillation should be not more than 10° so that oscillations are regular
- Allow the pendulum to swing until the oscillations are steady before taking readings so as to obtain a regular period of oscillation
- Allow the pendulum bob to swing for a few oscillations to ensure that it is along the vertical plane so as to obtain a regular period of oscillation
