Combined Science Form 1-2 Physics Notes
Data Presentation
Data is information such as facts and statistics gathered by scientists during experiments or research.
Scientists interpret data (understand and explain meaning) and use it to make conclusions about their experiments.
Data gathered need to be presented in a way that is not time consuming, e.g., visually or graphically.
Data can be qualitative (observations) or quantitative (statistical data).
Tallies
Tallies are unary numeral marks used for counting; useful for ongoing results (e.g., scores).
Not ideal for static text when numbers get large.
Tallies are typically clustered in groups of five for legibility and easy conversion to decimal.
Example (mass of Form 1 learners, mass in kg, and number of learners):
Clusters shown as: 1, 6, 11, 8, 4 corresponding to ranges 31–35, 36–40, 41–45, 46–50, 51–55.
Tables and graphs as data presentation tools
Tables provide clear, easy-to-read data with descriptive headings.
Each column/row should be labelled and may include units.
Example table: Favourite fruit types for Form One learners, with columns for fruit types and numbers of learners.
Bar graphs
Visual display using vertical bars on axes.
Used when data are in groups/categories (e.g., days of the week, types of transport, types of fruit).
Bar height represents values in the corresponding table.
Example: Banana, Mango, Marula, Apple with corresponding numbers; conclusion that bananas are most popular and apples least popular.
Measurement
Estimating quantities
An estimate is a guess close to the actual value based on knowledge or rough calculations; can be done before actual measurement.
Different people may give different estimates for the same quantity.
Example tasks include estimating:
Lengths (e.g., width of classroom door, length of classroom walls, height of desk).
Masses (e.g., mass of a science textbook, a pen, a beaker).
Temperatures (e.g., cold, warm, hot water).
Times (e.g., time to walk the length of the class, logic for boiling 100 ml of water).
Record all observations in a table with Estimation, Actual Measurement, and Accuracy.
Errors in measurement
Errors occur in all physical measurements; two common errors discussed:
Parallax error: reading error due to incorrect eye position; avoid by aligning eye with instrument pointer and scale.
Zero error: incorrect positioning of the zero point on the instrument.
Physical quantities and SI units
Physical quantity: a property of an object/substance that can be measured with a suitable instrument.
SI units are the international standard units used by scientists.
Reading measurement scales accurately requires correct eye position and proper scale interpretation.
Reading scales example: If a scale has 10 divisions between 0 and 1, each division represents 0.1 units.
Reading positions (A, B, C) may give different readings depending on alignment; the correct reading corresponds to proper eye position.
Converting units (SI prefixes and base units)
Prefixes: Kilo- (k) = 1000, Milli- (m) = 0.001, Centi- (c) = 0.01.
Length
SI unit: metre (m); other units: centimetre (cm), millimetre (mm).
100 cm = 1 m, 10 mm = 1 cm.
Conversions:
Metre to centimetre: 1\ \text{m} = 100\ \text{cm}
Centimetre to metre: 1\ \text{cm} = 0.01\ \text{m}
Mass
SI unit: kilogram (kg); other units: gram (g), milligram (mg).
1\ \text{kg} = 1000\ \text{g}; 1\ \text{g} = 0.001\ \text{kg}
Time
SI unit: second (s); other units: minute (min), hour (h).
1\text{h} = 60\ \text{min},\ 1\text{min} = 60\ \text{s},\ 1\text{h} = 3600\ \text{s}
Temperature
SI unit: Kelvin (K); other units: degrees Celsius (°C), degrees Fahrenheit (°F).
0^{\circ}\text{C} = 273\ \text{K}
Conversions (conceptual): °C to K add 273; K to °C subtract 273.
Measuring physical quantities
Mass of a liquid
A liquid cannot be weighed directly in a beaker; determine by difference:
mass of water = mass (beaker + water) − mass (empty beaker).
Volume of irregular objects (displacement method)
When an object is submerged in water, it displaces its own volume.
Overflow can method: fill overflow can to water level with bottom of spout; submerge object; measure displaced water volume as object volume.
If displacement can unavailable, use a measuring cylinder: read initial water volume, submerge object, read final volume, then
V{object} = V{final} - V_{initial}Volume of many small objects
Mass of many small objects divided by count to get mass per object (e.g., seeds).
Volume of water and seeds example
Given initial and final volumes, compute volume of seeds by subtraction and division.
Thickness of one sheet
Measure thickness of sheets, divide by number of sheets to obtain thickness per sheet; convert cm to mm if needed.
Density
Definition: Density is mass per unit volume.
Formula: D = \frac{m}{V}
Common units: g/cm³ or kg/m³.
Example problems (from notes):
Calculate density of glass if 120 cm³ of glass has mass 300 g.
A cylinder of aluminium with radius 7 cm, height 20 cm, mass 8.316 kg; calculate density of aluminium.
A beaker with a mass of 48 g contains 120 cm³ of copper(II) sulfate solution; combined mass is 174 g; determine density.
Force
Definition: A force is a push or a pull; it can deform, accelerate, change direction, or move an object.
Effects of forces include:
Distortion or deformation (change in shape/size)
Change in speed (acceleration or deceleration)
Change in direction
Change in position (movement)
Types of forces
Contact forces (mechanical): forces in direct contact (e.g., pushing, pulling, twisting).
Non-contact forces (action at a distance): e.g., gravity, magnetic, electrostatic.
Specific forces mentioned
Weight: force due to gravity on mass
Mechanical force: caused by movement (e.g., falling water)
Friction: force that opposes motion between two surfaces in contact; can slow or stop motion
Measuring force
Measured in Newtons (N) using a force meter or spring balance.
A force meter consists of a spring with a hook; the longer the stretched spring, the larger the reading (scale in N).
A spring balance converts mass to weight using gravity (≈ 10 N per kg):
1\ \text{kg} \approx 10\ \text{N}
Example: 100\ \text{g} \approx 1\ \text{N}
Balanced and unbalanced forces
If two equal forces act in opposite directions, the system is in equilibrium (no movement).
If forces are unbalanced, movement occurs in the direction of the larger force.
Resultant force is the sum/difference of forces along the same line; when the resultant is zero, the body is in equilibrium.
Direction of force is shown by arrows; larger arrows indicate larger forces.
Examples (practice problems listed in notes)
Example 1: A small cart pulled by 2 oxen with 200 N; friction 50 N (ground) and 75 N (wheel-axle). Find resultant force.
Example 2: A wheelbarrow pushed with 150 N; friction 30 N. Draw forces and find resultant force.
Moment of a Force
Moment (turning effect) about a fulcrum (pivot)
Depends on both the size of the force and its distance from the pivot (perpendicular distance).
Formula: M = F \times d where d is the perpendicular distance from the line of action of the force to the fulcrum.
Units: Newton metres (Nm).
The greater the force and/or the distance from the fulcrum, the greater the turning effect.
The principle of moments
For equilibrium (balanced), the sum of clockwise moments equals the sum of anticlockwise moments:
\sum (Fi \times di){clockwise} = \sum (Fj \times dj){anticlockwise}
Examples (practice problems)
See problems involving balancing see-saws with given masses and distances to find unknown positions.
Friction
Friction is a force that opposes motion between two surfaces in contact.
Conditions for motion
An object stays stationary if the frictional force is greater than the pushing force.
An object moves only if the pushing/pulling force exceeds friction.
Factors affecting friction
Nature of surfaces (rougher surfaces increase friction)
Road surfaces are rough to improve friction and prevent slipping.
Measuring friction
Tie a string around a brick; use a force meter to pull and record the maximum force before movement (static friction).
Then pull to slide with minimum force to keep moving (kinetic friction).
Static vs kinetic friction
Static friction is the maximum opposing force just before movement starts.
Once movement starts, a smaller force is often enough to keep it moving (kinetic friction).
Applications and ways to reduce friction
Lubrication, rollers, ball bearings, polishing surfaces, wheels.
Simple Machines
Definition: A machine is a device that makes work easier (e.g., levers, pulleys, inclined planes, gears, wheel and axle).
A machine converts energy and magnifies a small force into a larger one to do work.
Levers
A lever is a bar that turns about a pivot (fulcrum).
In a lever, an effort force is applied at one end to overcome a resisting load at the other.
Fulcrum is the pivot point.
Classes of levers
First class: fulcrum between load and effort (e.g., crowbars, scissors, claw hammer, pliers).
Second class: load between fulcrum and effort (e.g., wheelbarrow, nutcracker, bottle opener).
Third class: effort between fulcrum and load (e.g., hoe, fishing rod, tongs, spade).
Energy
What is energy?
The ability to do work.
Forms of energy discussed
Kinetic energy (motion): more energy with faster movement.
Heat energy (thermal energy): related to internal energy; transferred by conduction, convection, or radiation.
Electrical energy: electrons flowing through a conductor; can be converted to heat/light, etc.
Chemical energy: stored in fuels/food; released via chemical reactions (e.g., respiration); batteries store chemical energy.
Potential energy: stored energy due to position or condition (e.g., gravitational, elastic, chemical).
Light energy: enables vision and photosynthesis; main source is the Sun.
Sources of energy
Renewable: wind, bio-fuels, solar, hydropower.
Non-renewable: fossil fuels, nuclear.
Forms of potential energy
Gravitational potential energy: due to position relative to Earth (e.g., water behind a dam).
Elastic potential energy: stored in stretched/squeezed objects (e.g., bowstring, wound spring).
Chemical potential energy: stored in chemical bonds (e.g., fuels, foods).
Energy conversion chains (examples)
Green plants: solar energy → chemical energy in carbohydrates.
Catapult: chemical energy → kinetic energy → potential energy → kinetic energy.
Dynamo: kinetic energy → electrical energy → light energy.
Bulb: electrical energy → light and heat energy.
Solar panel: solar energy → electrical energy → chemical energy in cells.
Energy conservation
The law of conservation of energy: total energy of a closed system is constant; energy is neither created nor destroyed, only transformed.
Energy conversion may involve work or energy transfer.
Magnetism
Magnets and properties
Magnets produce magnetic force; typically made of iron or steel.
Properties:
Can attract magnetic materials
Have two poles (north and south)
Have a magnetic field
Exert attractive and repulsive forces
Types of magnets
Bar magnet: straight bar; weaker on the sides; stronger at ends.
Horse-shoe magnet (U-shaped): poles facing same direction; stronger around both poles.
C magnets: curved shape; used in motors, washers, fridges, speakers, etc.
Electromagnets (E magnets)
Magnetic field is produced by electric current in a coil around a soft iron core.
When current flows, core becomes magnetised.
Earth as a magnet
Earth has a magnetic field with north and south poles; field lines run from magnetic north to magnetic south.
The Earth’s magnetic and geographic poles are opposite.
Magnetic materials vs non-magnetic materials
Magnetic materials: attracted by magnets (e.g., iron, nickel, cobalt).
Non-magnetic materials: not attracted (e.g., wood, rubber, plastic, glass, copper, aluminium).
Magnetic fields and field lines
Field lines show direction and strength; direction typically from north to south.
Iron filings can illustrate the pattern of a magnetic field around a bar magnet.
Plotting compass can be used to map magnetic field lines around magnets.
Field strength and interaction
Magnetic field gets weaker as distance from the magnet increases.
When magnets are brought together, field lines interact, causing attraction or repulsion depending on alignment.
Electricity
Static electricity
Charges buildup through rubbing; like charges repel, unlike charges attract.
Examples: rubbing polythene with cloth leaves it negatively charged; rubbing Perspex leaves it positively charged.
Only electrons move; protons stay fixed.
Current electricity and circuit symbols
DC circuits use a closed path for current; a circuit diagram uses standard symbols for components.
Common circuit symbols (as shown in notes) include cells, switches, resistors, light bulbs, fuses, ammeters, voltmeters, and variable resistors.
Conductors and insulators
Conductors allow electricity to flow (e.g., copper, carbon, salt water).
Insulators do not conduct well (e.g., rubber, plastic, wood, glass, pure water).
Electrolytes conduct electricity due to chemical changes in solution.
Most metals are conductors; most non-metals are insulators except graphite (carbon).
Simple circuit construction and testing conductors
Build a simple circuit with a battery, wires, and a light bulb.
Test different materials with crocodile clips to determine conductors vs insulators; a light bulb lights up if a material conducts.
Measuring current, voltage, and power
Current (I): flow of charge; measured with an ammeter; unit is the ampere (A).
Voltage (V): potential difference; measured with a voltmeter; unit is the volt (V).
An ammeter is placed in series; voltmeter in parallel with the component being measured.
Metrological principle: voltmeters have high resistance; ammeters should have low resistance to avoid affecting the circuit.
Power in circuits
Electrical power is the rate at which electrical energy is converted to other forms.
Formula: P = V I where P is power, V is voltage, I is current.
Unit of power: watt (W).
Examples of applying power formula
What is the power of a bulb drawing 0.25 A from a 240 V supply?
What current is drawn by a 1.5 kW heater on a 240 V supply?
What voltage is needed for a 0.5 A current to pass through a 100 W bulb?
Conductors, insulators, and electrolytes recap
Test multiple materials to determine their conductivity.
Electrolytes are solutions that conduct electricity due to ion movement.
Quick Reference Formulas (from notes)
Density
D = \frac{m}{V}
Volume (irregular object by displacement)
V{object} = V{final} - V_{initial}
Moment of a force (turning effect)
M = F \times d
Equilibrium (principle of moments)
Clockwise moments = Anticlockwise moments
\sum Fi di\big|{clockwise} = \sum Fj dj\big|{anticlockwise}
Work (energy transfer)
W = F \times d
Power in circuits
P = V I
Length/volume/temperature conversions (selected)
1\ \text{m} = 100\ \text{cm}
1\ \text{cm} = 0.01\ \text{m}
1\ \text{kg} = 1000\ \text{g}
1\ \text{h} = 60\ \text{min}, \ 1\ \text{min} = 60\ \text{s}
0^{\circ}\text{C} = 273\ \text{K}
Notes and terms often seen in these topics:
Qualitative vs quantitative data
Parallax error and zero error in measurement
SI units and base units (m, kg, s, K)
Units for force (N), energy (J), power (W)
Types of energy and energy conversions
Different classes of levers and the idea of effort, load, and fulcrum
The earth’s magnetic field and how to demonstrate magnetic field lines with filings or a plotting compass
Static vs dynamic friction and methods to reduce friction
Displacement method for volume measurement and density calculations