Physic form 4 note

CHAPTER 1 INTRODUCTION TO PHYSICS

1.1 Understanding Physics
Physics: Study of all natural phenomenon
Physics is a branch of science centred on the study of matter, energy, and the connection them.

1.2 Understanding Base Quantities and Derived Quantities/ 1.3 Understanding Scalar and Vector Quantities

Symbol Magnitude

Mass, m = 50 kg Unit

Physical Quantities
- quantities that can be measured

Base Quantities SI Unit Derived Quantities SI Unit Scalar Quantities SI Unit Vector Quantities SI Unit
- quantities that cannot be - combination of basic - Quantities with magnitude - Quantities with magnitude
kg m
defined in any other form m quantities through only and direction m s-1
of physical quantities s multiplication or division m s-2
Mass, m A Density kg m-3 Distance, s m Displacement, s N
Length, l K Volume m3 Speed, v m s-1 Velocity, v kg ms-1
Time, t Force N Work done, W J Acceleration, a
Electric Current, I Energy J Power, P W Weight, W
Temperature, θ Pressure Pa Voltage, V V Momentum, p

Prefixes Example 1
multiple
Prefix Symbol Sub- Prefix Symbol The diameter of a particle is 250 m. What is its diameter in cm?
1012 multiple
109 tera T 10-1 deci d A 2.5 x 10-2 B 2.5 x 10-4 C 2.5 x 10-6 D 2.5 x 10-8
106 giga G 10-2 centi c
103 mega M 10-3 milli m Example 2
102 kilo k 10-6 micro µ
101 hecto h 10-9 nano n The density of a substance is 10 918 kg m−3. State the density in g cm−3.
deca da 10-12 pico p
A 0.10918 B 1.0918 C 10.918 D 109.18

Example 3

An object moves along a straight line for time, t. The length of the line, s is given

Scientific notation is used for large and small numbers. s  1 gt2
by the equation 2 . The SI unit of g is
The general form of a number in the scientific notation is
A X 10N A m2 s2 B m s-2 C s-1 D s-2 m

1.4 Understanding measurements / 1.5 Analysing Scientific Investigations Micrometer Screw Gauge
Vernier Calipers

Accurate and Not accurate Not Accurate and Accuracy – the degree of closeness of the measurement to the true value.
Consistent But Consistent Not Consistent
Consistency- the ability of an instrument to measure consistently with little or no
Relationship in a Graph relative deviation among readings.

Sensitivity – the ability to detect small changes in the quantity measured.

y is directly proportional to x y is increases linearly with x y is decreases linearly with x y increases as x increases y is inversely proportional to x

CHAPTER 2 FORCES AND MOTION

2.1 Analysing linear motion / 2.2 Analysing motion graphs

Linear Motion Motion Graph

Scalar Quantities Vector Quantities Displacement-time graph Velocity-time graph
Distance Displacement s/m v/ ms-1
Total path length travelled from one Distance between two locations
12 A B 8P Q

location to another. measured along the shortest path A1
Average speed = Total distance(m) connecting them, in a specified
direction. C t/S R t/S
6 8 10
Average velocity = Total displacement(m) O3 O2 4 5 A2 6

time(s) time(s)

Acceleration = final velocity – initial velocity -8 D -6 S
time taken

Equation of Linear Motion

v  u  at Example D O/C A/B O PQ R
A bus moving with an initial velocity 50 m s-1 S
s  (u  v) t O-A Constant velocity
2 comes to a stop. The braking distance of the bus is A-B At rest/ zero velocity O-P Constant acceleration/
B-C Constant negative velocity/ Increasing velocity
s  ut  1 at2 500 m. Determine the deceleration of the bus.
2 A. 2.5 m s-2 Moving in opposite direction P-Q Constant velocity
B. 10.0 m s-2 C-D Constant negative velocity/ Q-R Constant deceleration/
v2  u 2  2as C. 25.0 m s-2
decreasing velocity

Ticker tape and Ticker Timer Moving in opposite direction R-S Constant negative

10 ticks Gradient,m = − acceleration/ Increasing
time taken = − velocity in opposite direction

= velocity Gradient,m = acceleration
Area under graph
Displacement = Velocity = Distance = A1 + A2
Displacement = A1 - A2
Example
1) Find the velocity of

a) VOA = 1) Acceleration, aQR =

v= u= v= u= b) VCD = 2) Distance =
2) Distance = 3) Displacement =
t= t= 3) Displacement = 4) Average velocity =
a= a=

2.3 Understanding inertia/ 2.4 Analysing momentum / 2.6 Analysing impulse and impulsive force
2.7 Being aware of the need for safety features in vehicles / 2.8 Understanding gravity

Inertia – the tendency of an object to resist change in motion. Impulse, Ft = mv – mu −
SI unit = kg ms-1
The greater the mass, the greater the inertia Impulsive force, F =
Application of Inertia SI unit = kg ms-2
1) Drying a wet umbrella
Application of Impulsive Force
- The umbrella is rotated and when stopped abruptly, the droplet of water on
the umbrella is shaken off due to inertia. 1) Goal keepers will wear gloves to increase the collision time. This will reduce the
2) Pouring tomato sauce out of the bottle.
- When the bottle is given a quick downward jerk and stopped suddenly, the impulsive force.
inertia of the sauce tend to move it downwards and out of the bottle.
3) Tighten a hammer head 2) A football must have enough air pressure in it so the contact time is short. The
4) Running zig-zig when chased by a bull.
impulsive force acted on the ball will be bigger and the ball will move faster and
Momentum, p = mass, m x velocity, v
S. I unit = kg ms-1 further.

Principle of Conservation of Momentum 3) Bending of legs.
In the absence of an external force, the total momentum of a system remains
unchanged. 4)Hammering a nail into the wall.

m1u1 + m2u2 = m1v1 + m2v2 Safety Features

Safety seat belt To prevent the passenger from being thrown out of the car.

Side impact bar To minimize the force acting from a side- on collision.

Anti-lock braking To prevent wheel lock and skidding, thus contributing to

system safer braking

Crumple zone To increase the time interval of impact so that the resultant
impulsive force is reduced.

Elastic Collision Inelastic Collision Explosion Gravity

Condition Two objects collide move Two objects combine Two or more bodies in 1) Free fall is when an object is fall under the force of gravity only.
Diagram apart again after a contact will be separate
Formula collision and stop or move after the collision 2) The gravitational field is the region around the earth in which an object

together with a common experiences a force towards the centre of the earth.

u1 u2 velocity after a collision
m1 m2
u1 u2 m2 m1 m2 Weight, W = mass, m x acceleration due to gravity, g
V1 m1 v2 m1 V1 v2 S.I unit = kg ms-2
m2
V m1 m2
m1 m2

m1u1 + m2u2 = m1v1 + m2v2 m1u1 + m2u2 = (m1 + m2)v 0 = m1v1 + m2v2 At rest/ Accelerate upward Accelerate downward
m1v1 = - m2v2 Constant velocity

KE conserved Not conserved Not conserved R
conserved a
Etotal conserved conserved conserved R R
a=0 a W = mg
ptotal conserved conserved
W = mg W=mg R = mg - ma
Application R = mg
R = mg + ma
1) Propulsion of jet engine/ launching of a rocket

2) Rifle or Canon being fired

3) Movement of a squid

2.5 Understanding the effects of a force/ 2.9 Analysing forces in equilibrium

1) Force is a push or pull.

2) Newton’s Second Law of Motion - The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and

the mass of the object. The acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object.

3) Newton’s Third Law of Motion - For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces

acting on the two interacting objects.

Balanced forces/ Forces in Equilibrium Unbalanced Forces Fnet = ma
- Net force is equal to zero - Net force is produced SI unit = Newton, N
Fnet = 0 N

Addition of Forces Resolution of Forces

cos θ =


Fy F Fx = F cos θ

θ sin θ =
Fx

Fy = F sin θ

Object at rest Object move with Triangle Method Parallelogram Method Inclined Plane
R constant velocity
- Normally use to find the - Must use scale drawing. (eg. 1
W resultant force for two cm: 5 N)
forces which are
perpendicular to each other - The magnitude can be find by
measure the length.
Fnet Fy
- Measured the angle by using
protractor.

Normal force, R = Weight, W Fx Component of weight parallel to the plane, Fp = mg sin θ

Lift, L = Weight, W = √ + Component of weight normal to the plane, FN = mg cos θ
Thrust, T = Drag, D
ta Example * If object is in equilibrium
Type equation here.θ
Type equation here. Fp = F, FN = N

Tsin45+Tsin30 = 0.75 a) Find a
T = 0.625 N mg sin 40 = ma
a = 6.43 ms-2
b) Find R
R = mg cos 40

= 15.32 N

Calculate the tension in
both the stings.

2.10 Understanding work, energy, power and efficiency /2.11 Appreciating the importance of maximizing the efficiency of devices /2.12 Understanding elasticity

Term/ Definition Formula and Units 1) Elasticity - A property of matter that enables an object to return to its
1. Work Done, W W=Fxs
original size and shape when the force that was acting on it is removed.
Product of the applied force and the W = Fs cos ө
distance moved in the direction of the SI Unit is Joule (J) or (Nm) Graph Law/ Formula
force.
2. Kinetic Energy, Ek Force, F vs extension, x Hooke’s Law
Energy possessed by an object due to its
motion. Ek = ½ mv2 The extension of a spring is directly proportional
3. Gravitational Potential Energy, Ep SI Unit is Joule (J)
Energy possessed by an object due to its to the applied force provided the elastic limit is
position.
4. Elastic Potential Energy, Ee not exceeded.
Energy stored in elastic object.
Ep = mgh Gradient, m = Spring constant, k =
5. Power, P SI Unit is Joule (J)
- The rate at which work is done. SI unit = Nm-1
- The rate of change of energy.
Area under the graph = Elastic Potential Energy
6. Efficiency, Ɛ
The ratio of the useful output to the Ee = Ee =
energy input of a device.

= Factors affecting Elasticity

SI unit is Joule (J) or (Nm) Factor Change in factor Less stiff More stiff

P  W  Fs  Fv (more elastic) (less elastic)
tt
Length Shorter spring 

SI unit is watt (W) or (Js-1) Longer spring 
Smaller diameter
Diameter of spring 
Input of energy
Ɛ = x 100%

= x 100% Larger diameter 

Principle of Conservation of Energy Thickness of spring wire Smaller diameter 

Energy cannot be created or destroyed, Larger diameter 
but it can transform from one form to another form.

Example Types of material The elasticity changes with the type of material
A trolley of mass 1.2 kg can move in a railroad ABCDE as shown in Diagram 3. At point A, the
trolley has an initial speed of 5.0 m s-1. Example
(a) What is the total energy acquired by the trolley
Diagram shows a system of three identical springs.
at A?
The original length of each spring is 10 cm. It is stretched
(b) What is the speed of the trolley at D?
to 13 cm when it loaded with mass of 50 g.

What is the total length of spring, X cm when the mass 100g?

(c) What is the kinetic energy of the trolley at E?

CHAPTER 3 FORCES AND PRESSURE

3.1 Understanding Pressure/ 3.2 Understanding Pressure in Liquid/ 3.3 Understanding Gas Pressure And Atmospheric Pressure

Pressure Pressure in Liquid Gas Pressure And Atmospheric Pressure

Definition: Formula: Definition:
Perpendicular force per unit area acting on a surface. The atmospheric pressure is caused by the weight of the
Formula: = atmosphere on the Earth’s surface.
S.I unit: Pascal, Pa
Gas pressure is the force per unit area exerted by the
= Pressure in liquids acts in all directions. gas molecules as they collide with the walls of their
S.I unit : Pascal, Pa or Nm-2 container.
Factors that Formula:
Smaller surface area, higher pressure
Smaller force, lower pressure affects PLiquid doesn’t affects PLiquid Patm = 76 cm Hg = 1 atm = 1 x 105 Pa

depth of liquid, h shape

density of liquid, ρ size

gravitational field

strength, g

Application

High Pressure Low Pressure 1) The wall of the water dam 1) The syringe
The wall of a dam is much thicker at the bottom than Pulling up the piston reduces the atmospheric pressure
AP AP at the top because it must withstand the increased inside the piston. The atmospheric pressure on the
lateral pressure in depths of the water. liquid surface then pushes the liquid up into the syringe.
1) Studs 1) Wider tires 2) The position of water tank 2) The vacuum cleaner
Normally a water tank is placed at higher level so as A vacuum cleaner produces partial vacuum. The fan
The studs on a football A tractor moving on soft to supply water at greater pressure. inside the cylinder blows air out of the vents hence
3) The body of the submarine produce low pressure. The atmospheric pressure
boot have only a small ground has wide tires to Submarine is built with thick wall so as to withstand outside then pushes air up the cleaner hose, carrying
enormous pressure at greater depth. dust and dirt with it.
area of contact with the reduce the pressure on the 4) The position of intravenous drips 3) The straw
The liquid solution is at a higher pressure so it has 4) The plunger/ rubber sucker
ground. The pressure ground so that they not sufficient pressure to flow into the veins of the
patient. Simple barometer Manometer
under the studs is high sink into the ground. Experiment:

enough for them to sink

into the ground, which

gives extra grip.

2) Knife/ needle/ nail 2) Shoulder pad/ seat belt

A sharp knife has a very A wide shoulder pad of a

small surface area on its heavy bag will reduce the

cutting edge so that pressure exerted on the

high pressure can be shoulder of the person

exerted to cut the carrying the bag. Pgas =

meat. P:
J= K=
* Unit for area : 1 cm2 = 10- 4 m2

Unit for force: Newton, N 1 kg = 10 N

3.4 Applying Pascal’s principle/ 3.5 Applying Archimedes’ principle/ 3.6 Understanding Bernoulli’s principle

Pascal’s principle Archimedes’ principle Bernoulli’s principle

Definition: Definition: Definition:
Pascal’s principle states that when pressure is Archimedes’ Principle state that when an object is Bernoulli’s principle states that the pressure of a moving
applied to an enclosed fluid, the pressure will be immersed in a fluid (a liquid or a gas) ,the buoyant force liquid decreases as the speed of the fluid increases and
transmitted equally throughout the whole (upthrust force) on the object is equal to the weight of vice versa.
enclosed fluid. fluid displaced by the object. Idea: (Venturi tube)
Formula:

1. Buoyant force, FB = Weight of fluid displaced

= = 2. Buoyant force = ρVg
= =
3. FB = Weight of object – weight of object

in air in water

S.I unit: Newton, N

1) Hydraulic Jack Application 1) Bunsen Burner/ Carburettor
When the handle is pulled, 1) Plimsoll line When the jet of gas flows out from the nozzle with high
valve P is still closed and valve The density of sea water varies with location. It is to velocity, the pressure in the Bunsen burner becomes
Q opens so the pressure can be ensure that a ship is loaded within safe limits, the Plimsoll low. A higher external atmospheric pressure will be
sent to the larger piston. The line marked on the body of the ship acts as a guide. sucked into the air hole and be mixed with the gas,
large piston will rise. While the 2) Rise or sink of a submarine/ hot air balloon complete combustion occurs.
small piston is pulled out, valve When the ballast tanks are filled with water, the buoyant 2) Spray
Q closes and valve P opens so that the oil in the force is smaller than the weight of the submarine. The When the piston is pushed, air is forced out through the
tank enter into the hydraulic cylinder submarine sinks. When the ballast tanks are filled with jet of gas at a high speed, the pressure of the moving air
heavy load. air, the FB is larger than the weight of the submarine. The decreases as the speed of the air increases. The higher
2) Hydraulic brake submarine rises. atmospheric pressure in the insect poison container will
A small force acting at the pedal can transmit a 3) Hydrometer push the liquid up through the narrow tube.
large force to all wheels simultaneously to stop Hydrometer is a device with a calibrated scale to measure 3) Aerofoil
the car. It is because the pressure will be the density of a liquid. Since the weight of the The path of air is longer over the upper surface than the
transferred through the pedal brake liquid to hydrometer equals the weight of the liquid it displaces, a lower, and therefore the speed is greater on the upper
car’s tyre. denser liquid will have a smaller volume of it displaces. surface. The lift is produced by the difference in
3) Lifting crane 4) Cartesian diver pressure between the two surfaces.

4.2 UNDERSTANDING SPECIFIC HEAT CAPACITY/ 4.3 UNDERSTANDING SPECIFIC LATENT HEAT

SPECIFIC HEAT CAPACITY, c Heating Curve (heat is absorb) SPECIFIC LATENT HEAT

Definition: Solid Liquid Gas Definition:

The specific heat capacity of a The specific latent heat of fusion is the quantity of heat

substance is the quantity of heat energy energy required to change 1 kg of a substance from a

required to increase the temperature of solid to a liquid without a change in temperature.
a mass of 1 kg by 1 °C or 1 K.
The specific latent heat of vaporisation is the quantity of

heat energy required to change 1 kg of a substance

Formula: from liquid to gases without a change in temperature.

Formula:

= = = =



Application Solid -Liquid Liquid - Gas Application
1) Cooking Utensil 1) Sweating
Change in Temperature No Change in Temperature QR,ST
Frying pans, pots, kettles, electric iron and so
PQ, RS, TU The latent heat is absorbed to overcome the force When we are engaged in strenuous activities, sweating
on made of substances with low specific cools our bodies. The sweat evaporates and the bodies
The heat absorb use to of attraction between the particles. The energy heat is removed as the latent heat of vaporization, thus
heat capacities . This is because they can our bodies temperature is decreased.
increase the kinetic absorbed does not increase the kinetic energy of
quickly heated up when there is only small
energy of particles. So the the molecules, so the temperature remains
heat absorption.
temperature rises. constant.
2) The handle of the cooking utensil
The handle is made by the substances with Cooling Curve(heat is release) (2) Cooling Drinks
high specific heat capacities. This is because
these materials undergo a small heat change Gas Liquid Solid Drinks can be cooled by adding in several cubes of ice.
while heat is released or absorbed. So , the When the ice is melting, the latent heat of fusion is
handles are not too hot to be held by the absorbed from the drinks. The temperature of the
bare hands. drinks is lowered.
3) Coolant (Water)
In a car engine cooling system, water is Gas -Liquid Liquid - Solid (3) Steaming Food
circulated through pipes around the engine Food can be cooked by using steam. Food such as
block to absorb energy from the hot engine Change in Temperature No Change in Temperature cakes, eggs, fish, buns and others receive a large
and so to keep it cool. From the cylinder PQ, RS, TU QR,ST amount of energy when the latent heat of vaporization
block ,the water passes into radiator where Heat is released to the surroundings The latent heat that released to the of steam released from condensing steam.
it is cooled by air drawn in by radiator fan. and the kinetic energy of the particles surroundings is balanced by the heat
The cool water is re-circulated through the decreases, resulting in a fall in the liberated as the particles attract one
engine to absorb the heat and this cycle is temperature of the particles. another to form liquid/ solid.
repeated continuously while the engine is
running.
4)Land Breeze and Sea Breeze

4.1 UNDERSTANDING THERMAL EQUILIBRIUM/ 4.4 UNDERSTANDING GAS LAW

GAS LAW

Temperature Heat Definition: Formula: Graph:
Is the degree of hotness of a body Is a form of energy P1V1 = P2V2
Is a base quantity Is a derived quantity ∝ , constant T
The S.I. unit is K or 0C The S.I. unit is Joule(J) Boyle’s Law

Measured by thermometer Measured by Joulemeter Definition: PV Definition:
∝ , constant V ∝ , constant P
The principle of thermal equilibrium

Pressure’s Law T Charles’ Law

Formula: T must be in Formula:
= Kelvin =

°C + 273 = K

Graph: Graph:

Two bodies in thermal contact are said to be in thermal equilibrium when Boyle’s Law Application/ Experiment Pressure’s Law
its reach the same temperature and the net flow of heat between the two
bodies is zero. 1. The bubbles formed by a Charles’ Law 1.Car tyres after a long drive become
Application
Mercury Thermometer 1. Hot- air balloon

fish expand as they floats very firm

towards the surface.

The sensitivity of the thermometer can be increased by 2. Bicycle pump
1. using a thinner-walled glass bulb
2. reducing the diameter of the capillary tube

Mercury is used in the thermometer because
1. has a higher boiling point
2. does not stick to the glass
3. is opaque and therefore it is easier to read.
4. expands and contracts uniformly

Calibration of Thermometer

CHAPTER 5 LIGHT

Reflection and Refraction of Light

Phenomenon Reflection of Light Refraction of Light
Law/
1) The incident ray, the reflected ray and the normal to the point of 1) Phenomena where the direction of light is changed when it crosses
Definition
incidence, all lie in the same plane. the boundary between two materials of different optical densities.
Ray Diagram
2) The angle of incidence, i = The angle of reflection, r

Characteristic of Image

1) Virtual 2) Same size 3) Laterally inverted Refractive index, n =
2) Upright
4) Object distance, u = image distance, v

Total Internal Reflection

Natural Phenomenon – Mirage, rainbow Application – Periscope (Prism), optical fibre

1) i < c- refraction 1) The layers of air nearer the road warmer. 1) The periscope is built using two right-angled prisms.
2) i = c- refraction 2) The density of air decrease nearer to the road surface. 2) The critical angle of the glass prisms is 42°.
3) i > c- total internal reflection 3) The light travel from denser to less dense area. 3) Total internal reflection occurs when the light rays
4) The light refract away from the normal
Condition for Total Internal Reflection 5) When the angle of incidence exceed the critical angle, strike the inside face of a 45°angles with an angle of
1) Light must travel from denser medium to less dense incidence, I, greater than the critical angle, c,.
total internal reflection occurs 4) The image produced is upright and has the same
medium size as the object.
2) The angle of incident must be greater than the critical

angle

Curve Mirror vs Curve Lenses

APPLICATION OF LENSES

Compound Microscope Astronomical Telescope

Object place between f and 2f Position of object Object at infinity
Objective lens and eyepiece are both high power lenses (short Type of lens
focal length) Objective lens – low power (long focal length)
fe > fo focal length
Real, inverted, magnified First image Eyepiece – high power (short focal length)
Virtual, inverted, magnified Final image
s > fo + fe Distance between lens, s fo > fe
Linear magnification, M
M = mo x me Real, inverted, diminished

Virtual, inverted, magnified

s = fo + fe

M= f
0

f
e

APPLICATION OF LENSES

Projector Camera

Characteristic Explanation Lens: to focus a sharp image onto the film
mirror used is concave / draw the To focus light from the source to the Film: to record the image
mirror slide Diaphragm: to adjust the size of the aperture (control the brightness of image).
Curve side of the lenses facing each Light from the source is spread evenly to Shutter: to open and shut the camera so that the film is exposed only for a short
other/ draw the arrangement of the slide to form a bright image on the time.
lenses screen

The distance of slide from the So that the image formed is real and
projection slides is between f and 2f magnified
The slide should be placed inverted So that the image formed on the screen
is upright

Formula

Power of lens = 1 11 1
uv f
focal length(m)

Magnification = hi  v Types of lens Convex Lens Concave Lens
h0 u
Focal length, f Positive (+) Negative (-)
Object distance, u Positive (+) Positive (+)
Image distance, v Always negative (-)
Real (+)
Virtual (-)