SI
Units
Candidates should be able to give the symbols for the following physical quantities and, where indicated, state the
units in which they are measured.
,
,Terminology that is used in the alternative to practical paper
(Candidates will not be required to recall the specific definition of these terms in the
examinations.)
Key term Meaning
Dependent Dependent variables are the variables that are observed or measured in
variable a scientific experiment. Dependent variables may change based on
changes made to the independent variables.
Independent Independent variables are the variables that are changed in a scientific
variable experiment by the scientist. Changing an independent variable may
cause a change in the dependent variable.
Anomaly An anomaly is a value in a set of results that appears to be outside the
general pattern of the results, Eg : an extreme value that is either very
high or very low in comparison to others.
Validity of Experiment is valid if the experiment tests what it says it will test. The
experiment experiment must be a fair test where only the independent variable and
design dependent variable may change, and controlled variables are kept
constant range the maximum and minimum value of the independent or
dependent variables.
Reproducibility A measurement is reproducible if the same or similar result is obtained
when the measurement is made under either different conditions or by
a different method or in a different experiment.
Repeatability A measurement is repeatable if the same or similar result is obtained
when the measurement is repeated under the same conditions, using
the same method, within the same experiment.
Precision How close the measured values of a quantity are to each other.
Accuracy A measurement result is described as accurate if it is close to the true
value.
Measurement The difference between a measured value and the true value of a
error quantity.
True value The value that would be obtained in an ideal measurement.
1. General physics
1 Physical quantities and measuring techniques.
• A rule (ruler) is used to measure length for distances between two points correct to 1mm ; the SI unit for
length is the meter (m). Measuring tape is used to measure the distance more than one metre.
• To find out the volume of a regular object, you can use a mathematical formula, you just need to
make a couple of length measurements.
• To measure the volume of an irregular object you have to put the object into measuring cylinder with
water. When you add the object it displaces the water, making the water level rise. Measure
, this rise. This is the volume of your object.
To measure the time stopwatch or clock can be used.
Measuring the volume of an irregular object
To find the volume of irregular solid object, measure out a known volume of water with a measuring
cylinder ( V1 ) and drop the solid object in. Record the rise in the level of water ( V 2 ) . The difference
between the two measurements ( V 2 -V1 ) is the volume of the solid object.
V2
V1
Volume of the solid object is = V2 - V1
40cm3 - 30cm3=10cm3
Measuring the Time:
• An interval of time is measured using clocks and digital timers , the SI unit for time is the second(s)
digital timer
clock
How to record the reading of a stop watch
The following stop watch shows the time that start of lap and end of lap.
The time taken to complete the lap = end of lap – start of lap
=50s
Units
Candidates should be able to give the symbols for the following physical quantities and, where indicated, state the
units in which they are measured.
,
,Terminology that is used in the alternative to practical paper
(Candidates will not be required to recall the specific definition of these terms in the
examinations.)
Key term Meaning
Dependent Dependent variables are the variables that are observed or measured in
variable a scientific experiment. Dependent variables may change based on
changes made to the independent variables.
Independent Independent variables are the variables that are changed in a scientific
variable experiment by the scientist. Changing an independent variable may
cause a change in the dependent variable.
Anomaly An anomaly is a value in a set of results that appears to be outside the
general pattern of the results, Eg : an extreme value that is either very
high or very low in comparison to others.
Validity of Experiment is valid if the experiment tests what it says it will test. The
experiment experiment must be a fair test where only the independent variable and
design dependent variable may change, and controlled variables are kept
constant range the maximum and minimum value of the independent or
dependent variables.
Reproducibility A measurement is reproducible if the same or similar result is obtained
when the measurement is made under either different conditions or by
a different method or in a different experiment.
Repeatability A measurement is repeatable if the same or similar result is obtained
when the measurement is repeated under the same conditions, using
the same method, within the same experiment.
Precision How close the measured values of a quantity are to each other.
Accuracy A measurement result is described as accurate if it is close to the true
value.
Measurement The difference between a measured value and the true value of a
error quantity.
True value The value that would be obtained in an ideal measurement.
1. General physics
1 Physical quantities and measuring techniques.
• A rule (ruler) is used to measure length for distances between two points correct to 1mm ; the SI unit for
length is the meter (m). Measuring tape is used to measure the distance more than one metre.
• To find out the volume of a regular object, you can use a mathematical formula, you just need to
make a couple of length measurements.
• To measure the volume of an irregular object you have to put the object into measuring cylinder with
water. When you add the object it displaces the water, making the water level rise. Measure
, this rise. This is the volume of your object.
To measure the time stopwatch or clock can be used.
Measuring the volume of an irregular object
To find the volume of irregular solid object, measure out a known volume of water with a measuring
cylinder ( V1 ) and drop the solid object in. Record the rise in the level of water ( V 2 ) . The difference
between the two measurements ( V 2 -V1 ) is the volume of the solid object.
V2
V1
Volume of the solid object is = V2 - V1
40cm3 - 30cm3=10cm3
Measuring the Time:
• An interval of time is measured using clocks and digital timers , the SI unit for time is the second(s)
digital timer
clock
How to record the reading of a stop watch
The following stop watch shows the time that start of lap and end of lap.
The time taken to complete the lap = end of lap – start of lap
=50s
