general physics for igcse and olevel students pdf

IGCSE Physics 0625 notes for topic 1: General Physics 1
TOPIC 1
GENERAL PHYSICS
UNITS OF MEASUREMENT:
Measurement means comparing any physical quantity with a standard to determine its
relationship to standard. This standard is called unit. All measurable quantity expressed in
a) some number or magnitude and b) some unit
For example if the distance is 200km, 200 is the number or magnitude and km (kilometer) is the
unit.
Systems of Units:
There are three major systems of units.
1. M.K.S. system: meters – kilogram – second system used internationally. This system is
also called SI (system international) units.
2. F.P.S. system: foot – pound – second system use by British.
3. C.G.S. system: centimetre – gram – second system use by French.
Measurement of physical quantities – base units:
Length or distance (s):
The base unit of length or distance is meter (m). It is define as:
The meter is the length of the path travelled by light in vacuum during a time interval of 1/299
792 458 of a second.
The measurement of length is used to calculate the:
i. thickness of a thin wire using vernier calliper. (The
precision of length measurements can be increased by
using the devices that use sliding vernier scale.)
ii. area of square or rectangle = length and width
iii. area of triangle = ½ base x height
iv. volume of cube = length x width x height

2
v. volume of liquid = height in calibrated measuring cylinder
Mass (m):
It is the measure of the quantity of matter in an object and its unit is kilogram (kg) in SI units. It
depends on the number of molecules in the matter and their masses and does not depend on
gravity. Therefore an object would have same mass on Earth and on the Moon but different
weight because of the change of gravity. Gravity on the moon is 1/6th
of the gravity on earth.
Mass of an object can be measured by using spring balance (newton-meter), top pan balance or
lever balance. The international definition of mass is
It is equal to the mass of the international prototype of the kilogram made up of platinum-iridium
alloy kept at international bureau of weights and measurements in Paris.
Time (t):
It is the ordering or duration of events. The unit of time is second (s) which is defined as:
the particular frequency of electromagnetic spectrum given out by the common type of caesium
atom.
The common devices to measure the time or
duration of an event are clock and
stopwatch. In stopwatch, each second is
calibrated into one hundred part of a second
called centisecond. The precession of time
duration of an event can be improved by measuring the time for number
of events and dividing time by total number of events. For example to
measure the time period of a pendulum the time for ten swings should
be recorded and dividing the total time by ten to get the time for one
swing.
SPEED, VELOCITY AND ACCELERATION:
Speed:
Average speed is defined as the distance covered by an object in unit time.
=
=
The SI unit of speed is meters/second (m/s) and it has no definite direction.

Velocity:
Velocity is defined as the distance travelled by an object in specific direction in unit time.
velocity =
Distance moved in specific direction is called displacement therefore the above equation can be
written as
=
v
⃗ =
s
⃗
t
s = the displacement in meters (m)
t = total time in seconds (s)
v = velocity, the SI unit of velocity is meters/second (m/s)
The object is said to be in linear motion if it moves in straight line.
Acceleration:
Acceleration is the change of velocity of a body in unit time.
= or = −
Where u is the initial velocity and v is the final velocity. The SI unit of acceleration is meters per
second square (m/s2
). Acceleration is positive if the velocity is increasing and negative if the
velocity is decreasing and this is called retardation or deceleration.
Graphical representation of velocity, acceleration and
distance:
Velocity – time graphs:
 The curve line in speed time graph means that the object is
moving with non-uniform acceleration. The acceleration at
any point is the gradient to the tangent at that point.
 In velocity-time or speed-time graph the area under the
graph is total distance covered by the object.
 In velocity-time or speed-time graph the gradient of the line
is acceleration.

4
Distance – time graph:
Terminal Velocity:
The terminal velocity of an object falling towards the earth, is the
speed at which the downward gravitational force ‘w’ (i.e weight) is
equal and opposite to the air resistance which is pushing it upwards
which means that the there is not net force and therefore no
acceleration. At this speed, the object does not accelerate and falls at
constant speed. The terminal velocity whose value is depends upon
the size, shape, volume and weight of the object.
For example, the terminal velocity of a skydiver in a normal free-fall
position is at certain point when his weight is equal to air resistance.
The reason an object reaches a terminal velocity is that the air
resistance is directly proportional to the square of its speed. At low speeds the air resistance is
much less than the gravitational force and so the object accelerates. As it speeds up the air
resistance increases, until eventually it equals the weight. The diagrams below explain the
situation
v
w=m×g
Air resistance
a

MASS, WEIGHT AND DENSITY:
Mass:
Mass of an object is the measure of the amount of matter in it. The base unit of mass is the
kilogram (kg). 1kg =1000g
1 kilogram is the mass of a piece of platinum-iridium alloy at the office of weights and
measurements in Paris.
Weight:
The weight of an object is the force due to earth`s gravity. The nearer an object is to the centre of
the earth the more the earth attracts it. Since the earth is not a perfect sphere but flatter at the
poles, the weight of a body varies over the Earth’s surface. It is greater at the poles than at the
equator. The weight of an object of mass ‘m’ can be found by
= ×
Where ‘w’ is the weight in newtons, m is the mass in kilogram and g is the acceleration due to
gravity whose value is 9.81m/s2
or 10 m/s2
for IGCSE course.
Density:
It is defined as the mass per unit volume of a substance. The unit of density is kg/m3
or g/cm3
. It
is denoted by Greek symbol ρ (rhoo) and is calculated from the formula:
=
=
Density of regularly shaped solid: The mass can
be determined by top-pan balance and the volume
by multiplying length, width and height.
Density of irregularly shaped solid for e.g. rock:
The mass of the solid is determined by top-pan
balance. The volume of solid is obtained by
subtracting the value before and after immersing the
rock in a measuring cylinder containing water. This
method is called displacement method.
Density of liquid: The mass of an empty beaker is
found on a balance. A known volume of the liquid is
transferred from burette or measuring cylinder into the
beaker. The mass of beaker plus liquid is found and the
mass of liquid is obtained by subtraction.
Density of air: The mass of a 500 cm3
round-bottomed
flask full of air is found and then after removing the air
with a vacuum pump; the difference gives the mass of
air in the flask. The volume of air is found by filling the
flask with water and pouring it into a measuring
cylinder.
Mass on top-pan
balance
Mass in a measuring
cylinder containing
water

6
EFFECTS OF FORCE: EXTENSION / LOAD (FORCE)
INVESTIGATION
Force is a push and pull of an object. Force can change the direction of the movement and the
shape of an object. Force can extend the length of an object.
Hooke’s Law:
Robert Hooke was the first to investigate the
extension of the spring nearly 350 years ago. He
stated the law of extension of the spring/string
when stretching force is applied to it.
“The extension of a spring is directly
proportional to the force applied on it, provided
the elastic limit of the spring is not exceeded.”
Stretching force F is directly proportional (⋉) to
the extension x
F ⋉ x
F = kx
k is the spring constant. It is the force needed to cause the
extension of 1 meter.
k =
F
x
Hooke’s law holds when a force applied to a spring, a
straight metal wire, elastic band or cotton thread. If too
much load is applied to the spring it deforms and does not
return to its original length after removing the load. The
spring is said to have undergone plastic deformation; the
load applied has exceeded the elastic limit (E) or limit of
proportionality,
E
Total Extension (x)
Stretching
force
(F)

FORCE, MASS AND ACCELERATION:
Effect of forces:
Force is a push or a pull of an object and it is measured in newtons, N. Force is a vector quantity
which means it needs magnitude and direction to be fully expressed. It can be used for pushing
pulling, bending, stretching, squeezing and tearing. When force applied it can do following
actions on an object, it can:
 change the speed or velocity,
 change the direction of movement,
 change the shape.
Isaac Newton in his second law of motion described the relation between force applied on an
object, the mass of an object and its acceleration. The two parts of the law says that:
a) The net force applied on an object is directly proportional to the acceleration of an
object:
∝
∝
b) The mass of an object is inversely proportional to the acceleration of an object:
∝
1
∝
1
Combining the above relationships we get
=
Where ‘F’ is the net force applied in newtons, N, ‘m’ is the mass of an object in kilogram and ‘a’
is the acceleration in m/s2
.
One newton force is defined as the force applied on an object of mass one kilogram
which accelerates it with one meters per second square.
Circular motion of an object:
Any motion in a curved path represents accelerated motion,
and requires a force directed toward the center of curved
path. This force is called the centripetal force which means
"center seeking" force. Swinging a mass on a string requires
string tension T, and the mass will travel off in a tangential
straight line if the string breaks.
Turning effect of force - moment:
The turning effect of force is called moment of force or torque or simply moment (τ). The
moment of force depends on two things:
1. the size of the force and;
2. perpendicular distance from the force applied to the pivot.
The unit is the newton-meter (N.m)
F, Direction of the
force towards the
centre
v, Direction of the
velocity at
tangent of the

8
Moment of force = force × perpendicular distance of the force from pivot or fulcrum
= ×
Law of moments
When an object is in equilibrium the total clockwise moments about the pivot is equal to the total
anticlockwise moments about the same pivot.
Total Clockwise moment of force = Total Anticlockwise moment of force
Equilibrium:
A body is said to be in equilibrium if the resultant force or net force acting on it is zero it means it
has no acceleration. The equilibrium is static if the body’s velocity is zero and dynamic if it is in
constant motion.
Conditions of Equilibrium:
a) Sum of the forces in one direction is equal to the sum of forces in the opposite direction.
 Net horizontal Force = 0
 Net vertical Force = 0
b) The law of moment must apply: sum of clockwise
moment is equal to the sum of anticlockwise
net moment = 0
Types of Equilibrium:
Stable Equilibrium:
When the body is slightly disturbed and then released, it
returns to its previous position then it is in stable
equilibrium.

Unstable Equilibrium:
When a body is slightly disturbed and it moves further away from its previous position then it is
in unstable equilibrium.
Neutral Equilibrium:
When a body is slightly displaced and it stays at its new
position then it is called neutral equilibrium.
For example the plumb line is in stable equilibrium
because if you push it to one side, it returns to its original
position. It does this because when you push it to one side
its centre of gravity rises and gravity tries to pull it back to its lowest position.
The carefully balanced ruler on your finger is in unstable equilibrium, because if it moves
slightly, it’s centre of gravity falls and keeps on falling down.
The ball on a perfectly level table is in neutral equilibrium, because if
it is moved, its centre of gravity does not rise or fall.
Name the different kinds of equilibrium in this figure (a), (b) and (c).
Lever
Lever is a simple machine which is used to lift heavy weight with
small force. It is force multiplier.
CENTRE OF MASS OR CENTRE OF
GRAVITY:
The centre of gravity or centre of mass of an object is the
point through which the whole weight of an object seems
to act. The centre mass of a uniform ruler is at its centre.
The centre of a circular cardboard is its centre of mass.
The centre of mass of a regularly shaped body of the
same density throughout is at its centre. In other cases it
can be found by following experiment.
Centre of mass of a piece of flat
card (lamina) using plumb line:
Let a piece of card hang freely from a pin attached with
a stand. Hang the plumb line from the pin. Mark the
position of the plumb line by two crosses on the card.
Join the crosses with a ruler. Just as the plumb line
hangs with its centre of gravity vertically below the
pivot, so also will the card. This means that centre of
gravity of the card is somewhere on line. Rearrange the
card with pin through another hole and again mark the
vertical line. The only point that is on both lines is
where they cross, so this point must be the centre of
gravity.

10
Toppling or stability:
Stability is the extent to which an object resists toppling over. Stable objects do not topple over
easily. When designing vehicles, engineers try to design so that the centre of mass is as low as
possible. This makes vehicles less likely to turn over when going round corners. The stability of
an object can be increase by:
a) Lowering its centre of mass
b) Increasing the area of its base
Examples:
 Double Decker bus has heavy metal panels at its bottom to make it more stable
 Racing car has wider base and low centre of gravity.
Slope not steep enough for toppling to occur Object on verge of toppling here the object will topple
Which of these trucks will topple over?
In the opposite diagram what is the moment of force.
SCALARS AND VECTORS:
Scalars:
Scalars are those quantities that have magnitude (size) only. For example mass, length, distance,
energy, temperature and speed. Scalar may be added together by simple arithmetic.
Vectors:
Vectors are those quantities that have both the magnitude and direction. Examples
are force, velocity, acceleration, displacement. When two vectors are added the
direction of the vector must also be considered. The vector may be represented by a
line, the length of the line being the magnitude of the vector and direction of the line
is the direction of the vector.
Addition of two vectors (eg forces):
The addition of vectors is called the resultant of those vectors. The
resultant of two vectors in the same direction in straight line is found
simply by addition of their magnitude and the direction is same as the

direction of the two vectors.
The addition of vectors in opposite direction in straight line is the addition of a vector and a
negative vector. The direction of the resultant vector
will be direction of the vector with greater
magnitude.
Parallelogram method of vector addition:
When two vectors are not in the same plain then we
use parallelogram method of vector addition. In this
method of vector addition, the vectors are joined
from a common origin and the parallelogram is
constructed by drawing resultant R the diagonal of
the parallelogram drawn from the common origin.
WORK, ENERGY, POWER
Work:
Work is done when a force moves an object in the direction of the force applied. The work is
define as
Work done = force × distance moved in the direction of force
Work = F × s
Where F is the force in newton (N) and s is the distance moved in the direction of force in meters
(m). Work is a scalar quantity.
In terms of energy transfer, work done is a measure of the amount of energy transferred from one
form to another. When you move an object to a certain height, the chemical energy transferred
from your muscles to potential energy of an object.
The unit of work or energy is joule (J) and one joule is defined as the work done when a force of
1 newton (N) moves an object through the distance of 1 meter (m).
Some examples of work done:
 A woman pushes a trolley along for 3 meters with a force 50 N,
 A man pushes his car for 10 meters with a force 300 N,
 A boy lifts a brick weighing 50 N.
Distance, s in meters (m)
Force, F in
newtons (N)

12
Energy:
The ability of an object to do work is called its energy. When the work is done the energy is
transferred from one form to another. There are different forms of energy that we use in our daily
life. For example we get:
 heat energy or also called thermal energy and light energy from sun;
 chemical energy from petrol, oil, wood, coal etc;
 sound energy from the bang of two objects;
 nuclear energy from nuclear reaction of atoms and nucleus;
 electrical energy from running turbine by burning coal, petrol etc at the power stations;
 kinetic energy is the energy because of the motion of an object;
 gravitational potential energy is the stored energy in an object due to its position from the
ground.
 Elastic potential energy or strain energy in springs, coils or elastic objects is the stored energy
due to their change of shapes or positions.
The two main forms of energies are kinetic energy and potential energy. The unit of energy is
joules (J).
Some examples of energy conversion:
 A light bulb converts electrical energy to light energy;
 A moving car converts chemical energy from petrol to kinetic and heat energy;
 A drill machine converts electrical energy to kinetic energy.
 A mountain climber changes chemical energy from his muscles to potential energy.
Kinetic Energy Ek:
The kinetic energy is the energy of an object, because of its motion. i.e. the object possess kinetic
energy if it is in motion or if an object is moving then it has kinetic energy. The kinetic energy
can be expressed by equation;
= ½ × ×

Where Ek is the kinetic energy in joules (J) of a moving object, m is the mass in kilogram (kg)
and v is the speed in meters per second (m/s).
Since Ek is depends on v2
, a high-speed object has much higher Ek than the object that is moving
at low-speed.
Potential Energy Ep:
The potential energy of a body is the energy because of its position
from the ground or due change in its physical shape. When an
object of mass ‘m’ is moved to height ‘h’ above the Earth’s surface
it is considered to have some gravitational potential energy. It is
equal to the work done in moving the object at that height. The
gravitational potential energy can be expressed by equation:
Ep = m×g×h
Where Ep is the gravitational potential energy in joules (J), m is the
mass of an object in kilogram (kg), h is the height in meters (m) and
g is the acceleration due to gravity equal to 10 m/s2
.
The other potential energies are elastic potential energy in spring,
electrical potential energy due to electric charge etc.
The law of conservation of energy:
The Law of conservation of energy states that:
The energy may neither be created nor can it be destroyed. The sum of all the energies in a
system or in an experiment must remain constant.
We can also say that the total amount of energy in the universe is
constant, although energy can be transformed from one form to another.
The most commonly used example is the pendulum. In the figure the
two end positions have maximum potential energy (Ep) and position in
the middle has maximum kinetic energy (Ek).
Mathematically it can be written as
Change in Ek = change in Ep
or
Gain of Ek = Loss of Ep
or
Loss of Ek = Gain of Ep
mass m
mass m
Object start moving with velocity v
Force, F in
newtons (N)
mass m
mass m
h
W=mg

14
POWER:
Energy transfer or work done in one second by an object is called its power.
=
=
The unit of power is watt (W) and it is defined as a rate of doing work or energy transfer per
second. The larger units of power are
1 kilowatt = 1 kW = 1000 W = 103
W and 1 megawatt = 1 MW = 1000000 W = 106
W
ENERGY SOURCES:
Renewable energy source:
Renewable energy source is the one that is generated from natural resources—such as sunlight,
wind, waves, tides and geothermal heat—which means it can be received from nature forever. In
future when we will have short of coal and natural gas to produce electricity we will be mostly
relying on renewable energy sources. At current levels of use, oil and gas supplies will last for
about another 40 years, and coal supplies for another 300 years. The development of renewable
sources of energy is therefore becoming increasingly important.
Non-renewable energy source:
Non-renewable energy sources are those energy sources that are used up and cannot be replaced.
One day they are going to be finished. These are fossil fuels like coal, oil and natural gas and
nuclear fuel like uranium, polonium and thorium etc.
Energy in different forms:
Chemical Energy
The energy held in the bond between atoms in a
molecule is called chemical energy. Every bond has
a certain amount of energy. In a chemical reaction
when it requires energy to break old bonds and
create new one, in chemical language it is called
endothermic reaction. Similarly in a chemical reaction
when the energy releases than this process is called
exothermic reaction. The burning of fossil fuel in
presence of oxygen is an example of exothermic
reaction.
Hydroelectricity
It is the electricity obtained from hydropower. Most
hydroelectric power comes from the potential energy of
dammed water driving a water turbine and generator.
The energy extracted from water depends not only on

the volume but on the difference in height between the source and the water's
outflow. This height difference is called the head.
Wave energy:
Movement of waves going up and down can be used make the move the fan of the
generator which than generate electrical energy. It is difficult to produce on large
scale by can be use for small scale power stations.
Geothermal Energy:
Hot rocks under the ground heat water to produce steam. Cold water goes down
through one hole and hot steam shots out from other. The force of powerful steam
rotates the turbine which drives electric generators and produce electricity.
Nuclear Energy:
Another major form of energy is nuclear energy, the energy that is trapped inside each atom. One
of the laws of the universe is that matter and energy can't be created nor destroyed, but can be
interchanged. Nuclear energy is the energy released from the atomic nucleus. One example of
nuclear reaction is fission reaction. In this reaction the neutron strikes the heavy uranium nucleus,
breaks into two new nuclei and emit large amount of energy. It follows the conversion of mass to
energy from the equation by Albert Einstein, E = m×c². E is the energy converted or released; m
is the mass, and c the speed of light which is 3×108
m/s.
Solar Energy:
Solar energy can be converted directly or indirectly into other
forms of energy, such as heat and electricity. The major problems
with the solar energy are:
1) that it is not consistent with how it reaches the earth.
2) the large area required to collect it at a useful rate.
Solar energy is used for heating water for domestic use, space
heating of buildings, drying agricultural products, and generating
electrical energy. The device use to convert sunlight into electricity
is called solar cell. It is usually made from silicon alloys.
Advantages Disadvantages
Hydroelectric and
tidal energy
No pollution, no operative
cost except maintenance
Expensive to build, flooding and building dams
cause environmental damage
Wind energy by using
wind turbine
No pollution, no operative
cost except maintenance
Large, windy areas needed, not reliable, noisy,
Solar energy by using
solar panel
No pollution Very expensive to build, useful only in very
sunny areas, large area required
Geothermal from
earth’s rock
No pollution, reliable, cost
effective
Deep drilling expensive and difficult
Nuclear energy from
uranium
Very efficient and
powerful,
Nuclear wastes are very dangerous, very
expensive to build and maintain.
Fossil fuel from oil,
coal and gas
Powerful and efficient Limited supply, bad for environment

16
PRESSURE:
Pressure is defined as the force applied by an object on a unit area on its surrounding in contact
with it. It means that the lower the contact area, the more the pressure is. The unit of pressure is
newton per meter square (N/m2
) or more commonly used pascal (Pa).
Pressure =
Force
Area
P =
F
A
In the above figure all four glass tanks have same amount of water and therefore have same
weight but each one has different area of contact with surface. Tank A has contact area 6 m2
, tank
B has 8m2
, tank C has 12m2
and tank D has 24m2
contact area. It means the tank A applies the
highest pressure on the surface since it has the smallest contact area.
Mercury Barometer
It is a device use to measure the atmospheric pressure. It
consists of a glass column of about 78 cm in height, closed
at one end and open at the other. The open end is placed
upside down inside a mercury-filled container. The height
of the mercury in the column rises and adjusts until the
weight of the mercury inside the column balances the
atmospheric force due to air exerted on the mercury in the
container. The height of the mercury column balances
exactly at 76cm which is equivalent to the atmospheric
pressure outside the column. Hence
1 atm. = 76 cm Hg =760 mm Hg = 101.325kPa = 101325 Pa
Manometer:
A manometer is a device use to measure gas
pressure in a container. A simple barometer design
is a U-shape glass tube. The glass tube is filled
with a liquid, usually mercury as shown in figure
below. One side of the tube is connected to the gas
supply and other side left open. The gas exerted
pressure on one side and the atmospheric pressure
is on the other side difference of pressure ‘h’
created.
Pressure of gas inside the container in mm Hg = 760mm + difference in mercury height h

Pressure due to liquid:
A liquid held in a container exerts pressure on the inner walls of the container as well as on any
object that is inside the liquid. Following are the properties applied to any object in a liquid.
1. Pressure of liquid on an object acts equally in all direction,
2. Pressure of liquid increase with the increase of depth,
3. Pressure depends upon the density of the liquid,
4. Pressure does not depend upon the shape of the container.
The pressure due to liquid of density ρ and height h can be expressed by
= × × ℎ
Pascal vases:
Liquid poured in a set Pascal vases is the demonstration that
pressure depends on depth only and not on the shape of the
vessel. When a set of tubes of different shapes are connected
to a common source of water, the water reaches the same
level in all the tubes.

general physics for igcse and olevel students pdf

More Related Content

Similar to general physics for igcse and olevel students pdf (20)

More from saeed akhtar (7)

Recently uploaded (20)

general physics for igcse and olevel students pdf