FORM 4: 1.6 MEANINGS

ITEM	MEANING
PHYSICS	Physics is the study of natural phenomena and the properties of matter.
PHYSICAL QUANTITY	A physical quantity is a physical characteristic that can be measured.
BASE QUANTITY	Base quantity is quantity that cannot be defined in terms of other base quantities.
DERIVED QUANTITY	A derived quantity is one which is obtained by combining base quantities by multiplication, division or both these operations.
SCALAR QUANTITIES	Scalar quantities are quantities that have magnitude but no direction.
VECTOR QUANTITIES	Vector quantities are quantities that have both magnitude and direction.
CONSISTENCY	The consistency of a measuring instrument is its ability to register the same reading when a measurement is made repeatedly.
ACCURACY	Accuracy of a measurement is how close the value of the measurement to the actual value.
SENSITIVITY	Sensitivity of an instrument is its ability to detect a small change in the quantity to be measured.
ERROR	Error is the difference between the actual value of a quantity and the value obtained in measurement.
ZERO ERROR	Zero error is the systematic error that occurs when the pointer of the instrument does not return to zero when not in use.
PARALLAX ERROR	Parallax error is the random error that occurs due to the incorrect positioning of the eyes in taking reading.

EXPERIMENT: SIMPLE PENDULUM

FORM 4: 1.5 ANALYSING SCIENTIFIC INVESTIGATIONS

HYPOTHESIS

MV increases, RV increases/decreases.

VARIABLES

i)          MANIPULATED VARIABLE   :

ii)         RESPONDING VARIABLE                      :

iii)       CONSTANT VARIABLE                           :

TABULATION OF DATA

MV (unit)	RV (unit)	other variable (unit)

GRAPH

VERTICAL AND HORIZONTAL AXES

Label each axis by writing the symbol representing the variable and its unit. For example, l (cm).

CHOICE OF SCALE

i)        Use the following ratios when choosing a scale.

§  2 cm to represent 0.1 unit/1 unit/10 units/100 units

§  2 cm to represent 0.2 unit/2 units/ 20 units

§  2 cm to represent 0.5 unit/ 5 units/ 50 units

ii)       The scale chosen should give a graph that covers more than 75% of your graph paper.

iii)     Avoid odd scales such as 2 cm to represent 3 units/6 units/7 units

PLOTTING THE POINTS

Points should be plotted as accurately as possible with a ‘×’.

DRAWING THE LINE

i)        Since the points are plotted using experimental data which have errors, they usually do not form an exact straight line.

ii)       The best straight line needs to be drawn.

iii)     The points not on the line should be as near as possible to the line.

iv)     The number of points above the line is approximately equal to the number points below the line.

v)      Students are advised to not connecting all the points as it will produce line that is not smooth.

ANALYSING THE GRAPH 

FORM 4: 1.4 UNDERSTANDING MEASUREMENTS

THE MEANING OF CONSISTENCY

The consistency of a measuring instrument is its ability to register the same reading when a measurement is made repeatedly.

THE MEANING OF ACCURACY

Accuracy of a measurement is how close the value of the measurement to the actual value. 

                          

THE MEANING OF SENSITIVITY

Sensitivity of an instrument is its ability to detect a small change in the quantity to be measured.

MEASURING INSTRUMENTS	SMALLEST MEASUREMENT (cm)	DEGREE OF SENSITIVITY
metre rule	0.1	low
vernier callipers	0.01	medium
micrometer screw gauge	0.001	high

THE MEANING OF ERROR

Error is the difference between the actual value of a quantity and the value obtained in measurement.

THE MEANING OF SYSTEMATIC ERROR

Systematic error is the error that will produce the reading that is always higher or always smaller than the actual reading.

SYSTEMATIC ERRORS ARE DUE TO

i)                    error in calibration of instrument

ii)                   zero error of the instrument

iii)                 error in reaction time

iv)                 wrong assumption in measurement

THE MEANING OF RANDOM ERROR

Random error is the error that will produce inconsistent readings due to the carelessness of the observer in making a measurement.

RANDOM ERRORS ARE DUE TO

i)                    parallax error

ii)                   sudden change in ambient factors such as temperature and air circulation

HOW TO AVOID RANDOM ERRORS

Repeat the measurements several times and take the mean value.

THE MEANING OF ZERO ERROR

Zero error is the systematic error that occurs when the pointer of the instrument does not return to zero when not in use.

THE MEANING OF PARALLAX ERROR

Parallax error is the random error that occurs due to the incorrect positioning of the eyes in taking reading.

HOW TO AVOID PARALLAX ERRORS

Line of view must be normal to the plane of the scale when taking readings.

VERNIER CALLIPERS

HOW TO TAKE THE READING OF VERNIER CALLIPERS

i)                    Read the mark on the main scale proceeding the ‘0’ mark on the vernier scale.

ii)                   Read the mark on the vernier scale that is exactly in line with any mark on the main scale.

MICROMETER SCREW GAUGE

HOW TO TAKE THE READING OF MICROMETER SCREW GAUGE

i)                    Read the main scale reading at the edge of the thimble.

ii)                   Read the thimble scale reading at the horizontal reference line.

FORM 4: 1.3 UNDERSTANDING SCALAR AND VECTOR QUANTITIES

THE MEANING OF SCALAR QUANTITIES

Scalar quantities are quantities that have magnitude but no direction.

THE MEANING OF VECTOR QUANTITIES

Vector quantities are quantities that have both magnitude and direction.

EXAMPLES OF SCALAR AND VECTOR QUANTITIES

SCALAR QUANTITIES	VECTOR QUANTITIES
length	momentum
mass	weight
distance	displacement
work	pressure
temperature	impulse
time	impulsive force
volume	acceleration
speed	velocity
energy	gravitational acceleration
density	force

FORM 4: 1.2 UNDERSTANDING BASE QUANTITIES AND DERIVED QUANTITIES

THE MEANING OF PHYSICAL QUANTITY

A physical quantity is a physical characteristic that can be measured.

THE MEANING OF BASE QUANTITY

Base quantity is quantity that cannot be defined in terms of other base quantities.

BASE QUANTITY	QUANTITY SIMBOL	SI UNIT	UNIT SIMBOL
length	l	metre	m
mass	m	kilogram	kg
time	t	second	s
electric current	I	ampere	A
temperature	T	kelvin	K

THE MEANING OF DERIVED QUANTITY

A derived quantity is one which is obtained by combining base quantities by multiplication, division or both these operations.

PREFIXES

THE PURPOSE OF PREFIXES:to express some physical quantities those are either very big or very small

PREFIX	SYMBOL	VALUE
nano	n	10-9
micro	µ	10-6
milli	m	10-3
centi	c	10-2
deci	d	10-1
kilo	k	103
mega	M	106
giga	G	109

CONVERT OF UNITS

STANDARD FORM

A x 10ⁿ; where 1 ≤ A < 10 and n is an integer

EXPRESS NUMBER IN STANDARD FORM

i)                    0.0000002 m = 2.0 x 10^-7 m

ii)                   12760000 m = 1.276 x 10⁷ m