Momentum

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Momentum

The momentum of an object is its mass multiplied by its velocity.

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Equation for momentum

The equation for calculating momentum is:
- $p = mv$
- Momentum = mass × velocity

Units

Momentum is measured in kg m/s.
Velocity is measured in m/s.
Mass is measured in kg.

Conservation of momentum

The law of conservation of momentum says that momentum cannot be created or destroyed.
If two objects collide, the sum of momentum before the collision is equal to the sum of momentum after the collision.

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Equation for the conservation of momentum

The equation for the conservation of momentum is:
- $m_1u_1 + m_2u_2 = m_1v_1 + m_2v_2$
- (Mass 1 × initial velocity 1) + (mass 2 × initial velocity 2) = (mass 1 × final velocity 1) + (mass 2 × final velocity 2)
In other words, the sum of the momentums of the two objects that are colliding will remain the same after they have collided.

1Forces & Motion

1.1Basics of Motion

1.1.1Average Speed

1.1.2Acceleration

1.1.3Distance & Displacement

1.1.4Velocity

1.1.5Adding Vectors

1.1.6Distance-Time Graphs

1.1.7Speed-Time Graphs 1

1.1.8Speed-Time Graphs 2

1.1.9Initial & Final Speed, Acceleration, Distance

1.1.10Average Speed - Calculations

1.1.11Acceleration - Calculations

1.1.12Uniform Acceleration - Calculations

1.1.13Grade 9 - Motion

1.1.14Exam-Style Questions - Graphs of Motion

1.2Forces

1.2.1Contact & Non-Contact Forces

1.2.2Examples of Contact Forces

1.2.3Friction

1.2.4Newton's First Law

1.2.5Newton's Second Law

1.2.6Newton's Third Law

1.2.7Describing Forces

1.2.8Using Free Body Diagrams

1.3Effects of Forces

1.3.1Momentum - No Impulse

1.3.2Momentum

1.3.3Momentum: Law of Conservation

1.3.4Force & Momentum Change

1.3.5Momentum - Safety

1.3.6Change in Momentum - Calculations

1.3.7Momentum - Calculations

1.3.8Mass

1.3.9Weight

1.3.10Centre of Mass

1.3.11Gravity - Calculations

1.3.12Free Fall

1.3.13Air Resistance & Friction

1.3.14Graphs of Motion with Air Resistance

1.3.15Turning Effect

1.3.16Moments

1.3.17Equilibrium

1.3.18Moments - Calculations

1.3.19Exam-Style Questions - Moments

1.4Stopping Distance

1.4.1Stopping Distance

1.4.2Stopping Distance - Thinking Distance

1.4.3Stopping Distance - Braking Distance

1.5Forces & Elasticity

1.5.1Stretching, Bending & Compressing

1.5.2Elastic Deformation vs Inelastic Deformation

1.5.3Hooke's Law

1.5.4Hooke's Law - Equation

1.5.5Hooke's Law - Spring Experiments

1.5.6Hooke's Law - Calculations

1.5.7Elastic Potential - Calculations

1.5.8End of Topic Test - Forces

1.5.9Exam-Style Questions - Elastic Potential

2Electricity

2.1Electricity in Homes

2.1.1Mains Electricity

2.1.2Power Rating of Appliances

2.1.3National Grid

2.1.4AC/DC

2.1.5Electrical Safety

2.1.6Fuses

2.1.7Fuse Ratings

2.2Current & Potential Difference

2.2.1Current

2.2.2Current - Equation

2.2.3Current - Calculations

2.2.4Conductors & Insulators

2.2.5Electrical Conductors - Electrons

2.2.6Potential Difference

2.2.7Potential Difference - Equation

2.2.8Measurements in Circuits

2.2.9Voltage - Calculations

2.3Resistance & Power

2.3.1Resistance

2.3.2Ohm's Law

2.3.3Measuring Resistance

2.3.4Resistance & Ohms Law - Calculations

2.3.5Variable Resistance

2.3.6Current-Voltage Graph for a Resistor

2.3.7Electrical Work

2.3.8Power

2.3.9Heating Effect in Resistors

2.3.10Electrical Work - Calculations

2.3.11Exam-Style Questions - Resistance

2.4Electric Circuits

2.4.1Circuit Diagrams

2.4.2Circuit Symbols

2.4.3Diodes

2.4.4LDRs & Thermistors

2.4.5Series Circuits

2.4.6Resistors in Series

2.4.7Series Circuits - Calculations

2.4.8Parallel Circuits

2.4.9Parallel Circuits in Practice

2.4.10End of Topic Test - Electricity

2.4.11Grade 9 - Circuits

2.4.12Exam-Style Questions - Electrical Circuits

2.5Static Electricity

2.5.1Electric Charge

2.5.2Charging an Object

2.5.3Charged Objects

2.5.4Uses of Static Electricity

2.5.5Charge Dangers

2.5.6Calculating Power & Energy Transferred

3Waves

3.1Wave Basics

3.1.1Wave Basics

3.1.2Transverse Waves

3.1.3Longitudinal Waves

3.1.4Wave Frequency Formula

3.1.5Wavelength & Amplitude

3.1.6Wave Speed

3.1.7Wave Speed - Calculations

3.1.8Wave Frequency - Calculations

3.1.9Wavefronts

3.1.10Doppler Effect

3.1.11Exam-Style Questions - Wave Speed

3.2Waves at a Boundary

3.2.1Changing Wave Motion

3.2.2Reflection

3.2.3Refraction

3.2.4Angle of Refraction

3.2.5Refractive Index 1

3.2.6Refractive Index 2

3.2.7Total Internal Reflection

3.2.8Optic Fibres

3.3Electromagnetic Spectrum

3.3.1Properties of Electromagnetic Waves

3.3.2Gamma Rays

3.3.3X-Rays

3.3.4UV Light

3.3.5Visible Light

3.3.6Infrared Radiation

3.3.7Microwaves

3.3.8Radio Waves

3.3.9End of Topic Test - EM Waves

3.3.10Exam-Style Questions - Electromagnetic Wave Uses

3.4Sound Waves

3.4.1Sound Waves

3.4.2Sound Waves & Our Ears

3.4.3Sound as a Wave

3.4.4Signal Generators

3.4.5Sound Waves - Oscilloscope Traces

3.4.6Measuring the Speed of Sound - Experiment

3.4.7End of Topic Test - Waves

3.5Communications

3.5.1Digital & Analogue Signals

3.5.2Benefits of Digital Signals

4Energy Resources & Energy Transfers

4.1Energy Changes

4.1.1Energy Stores

4.1.2Conservation of Energy

4.1.3Examples of Energy Conversion

4.1.4Kinetic Energy Stored

4.1.5Gravitational Potential Energy Stored

4.1.6Elastic Potential Energy Stored

4.1.7Changes in Kinetic Energy - Calculations

4.1.8Changes in GPE - Calculations

4.1.9Changes in EPE - Calculations

4.1.10Mechanical Work Done

4.1.11Mechanical Work Done - Equation

4.1.12Power

4.1.13Mechanical Work - Calculations

4.1.14Electrical Work Done- Calculations

4.2Energy Losses & Efficiency

4.2.1Energy Wastage

4.2.2Energy Transfer Diagrams

4.2.3Efficiency

4.2.4Reducing Unwanted Energy Transfer

4.2.5Efficiency - Calculations

4.2.6Grade 9 - Energy & Efficiency

4.2.7Exam-Style Questions - Energy & Power

4.3Energy Resources

4.3.1Energy Resources

4.3.2Fossil Fuels

4.3.3Geothermal Energy

4.3.4Wind Energy

4.3.5Water Energy

4.3.6Tidal Energy

4.3.7Nuclear Energy

4.3.8Solar Energy

4.3.9Non-Renewable & Renewable Resources

4.3.10Renewable Energy

4.3.11Limits to Renewable Energy Resources

4.3.12End of Topic Test - Energy

4.4Thermal Processes

4.4.1Radiation

4.4.2Conduction

4.4.3Molecular Conduction

4.4.4Convection Currents

4.4.5Convection Currents - Examples

5Solids, Liquids & Gases

5.1Density & Pressure

5.1.1Density

5.1.2Density Equation

5.1.3Calculating Density

5.1.4Density - Calculations

5.1.5Pressure

5.1.6Atmospheric Pressure

5.1.7Pressure Difference

5.1.8Pressure - Calculations

5.2Changing State

5.2.1Changes of State

5.2.2States of Matter

5.2.3Specific Heat Capacity

5.2.4Exam-Style Questions - Specific Heat

5.2.5Internal Energy - Calculations

5.3Ideal Gases

5.3.1Kelvin Scale & Absolute Zero

5.3.2Temperature & the Kelvin Scale

5.3.3Properties of Gases

5.3.4Temperature Increase in a Gas

5.3.5End of Topic Test - Solids, Liquids & Gases

5.3.6Grade 9 - Solids, Liquids & Gases

6Magnetism & Electromagnetism

6.1Magnetism

6.1.1Magnetism

6.1.2Magnetic Materials

6.1.3Hard & Soft Magnets

6.1.4Induced Magnetism

6.1.5Magnetic Forces

6.1.6Magnetic Field Patterns

6.1.7Exam-Style Questions - Magnetic Fields

6.2Electromagnetism

6.2.1The Magnetic Effect of a Current

6.2.2Magnetic Field around a Coil of Wire

6.2.3Magnetic Field Strength

6.2.4The Motor Effect

6.2.5Direction of the Motor Effect

6.2.6The Catapult Experiment

6.2.7Force on a Current Carrying Wire

6.2.8DC Motors

6.2.9Loudspeakers

6.2.10Magnetic Flux - Calculations

6.3Electromagnetic Induction

6.3.1Electromagnetic Induction

6.3.2Induced Potential Difference

6.3.3Alternating Current - The Rotating-Coil Generator

6.4Transformers

6.4.1Transformers

6.4.2Transformer Equation

6.4.3Step-Up & Step-Down Transformers

6.4.4Principles of Transformer Operation

6.4.5High-Voltage Transmission & Transformers

6.4.6Transformers - Calculations

6.4.7Transformers 2 - Calculations

6.4.8Energy in Transformers

6.4.9Power Losses in Cables

6.4.10End of Topic Test - Magnetism

6.4.11Grade 9 - Transformers

6.4.12Exam-Style Questions - Transformers

7Radioactivity & Particles

7.1Atoms

7.1.1Atomic Model

7.1.2Structure of an Atom

7.1.3The Charges of Sub-Atomic Particles

7.1.4Alpha Particles

7.1.5The Model of the Atom

7.1.6Proton & Nucleon Numbers

7.1.7Atoms & Ions

7.1.8Isotopes 1

7.1.9Isotopes 2

7.1.10Carbon Nuclides

7.2Radioactivity

8Astrophysics

8.1Motion in the Universe

8.1.1The Solar System

8.1.2Gravitational Field Strength

8.1.3Orbits

8.1.4Orbital Motion

8.2Evolution of Stars

8.2.1Life Cycle of a Star like the Sun

8.2.2Life Cycle of a Star Much Bigger than the Sun

8.2.3Absolute Magnitude

8.2.4Hertzsprung-Russell Diagrams

8.2.5Exam-Style Questions - Life Cycle of a Star

8.3Cosmology

8.3.1The Big Bang

8.3.2Evidence for the Big Bang

8.3.3CMB Radiation

8.3.4End of Topic Test - Astrophysics

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