Introduction to Year 8 Physics — Full Notes 1. What is Physics? Physics is the study of matter, energy, motion, and forces. It explains how and why

Introduction to Year 8 Physics — Full Notes

1. What is Physics?

  • Physics is the study of matter, energy, motion, and forces.

  • It explains how and why things move, why objects fall, and how energy works.

  • Physics is everywhere: from walking, sports, electricity, to the movement of planets.

  • Fun fact: Physics helps us design roller coasters, cars, and even smartphones!

2. Forces and Motion

  • A force is a push or a pull on an object.

  • Measured in Newtons (N).

  • Formula: F = m × a (Force = Mass × Acceleration).

  • Types of forces:

    • Gravity: Pulls objects toward Earth

    • Friction: Resists motion

    • Tension: Force in a rope or string

    • Normal force: Supports objects against gravity

  • Examples: Pushing a swing, pulling a rope, sliding a book across a table.

  • Mnemonic: “F = ma” → Force moves mass with acceleration

3. Newton’s Laws of Motion

  1. First Law (Law of Inertia):

    • Objects stay still or keep moving unless acted on by a force.

    • Example: A ball won’t roll unless pushed.

  2. Second Law:

    • F = m × a

    • The more mass an object has, the more force needed to move it.

    • Example: Pushing an empty cart vs. a full cart.

  3. Third Law:

    • Every action has an equal and opposite reaction.

    • Example: Jumping off a boat pushes the boat backwards.

4. Gravity

  • Gravity is a force pulling objects toward the center of the Earth.

  • Weight formula: W = m × g (g = 9.8 m/s² on Earth)

  • On the Moon, gravity is weaker → you weigh less.

  • Gravity also controls orbits of planets, moons, and satellites.

  • Fun fact: Without gravity, everything would float into space!

5. Energy

  • Energy is the ability to do work.

  • Types of energy:

    • Kinetic: Energy of motion (moving car, flowing water)

    • Potential: Stored energy (stretched spring, elevated ball)

    • Heat/Thermal: Movement of particles (fire, sun)

    • Light/Radiant: Energy from light (bulbs, the Sun)

    • Sound: Vibrations traveling through air, water, or solids

  • Law of Conservation of Energy: Energy cannot be created or destroyed, only transformed.

  • Example: A roller coaster converts potential energy at the top to kinetic energy going down.

6. Energy Transformations

  • Energy changes form as it moves or is used.

  • Examples:

    • Dropping a ball: Potential → Kinetic

    • Battery powering a bulb: Chemical → Electrical → Light + Heat

    • Solar panels: Light → Electrical

  • Mnemonic to remember types:

    • Kids Play Hard So Laugh → Kinetic, Potential, Heat, Sound, Light

7. Heat Energy

  • Heat moves from hot → cold spontaneously.

  • Three main ways heat moves:

    1. Conduction: Through direct contact (metal spoon in hot water)

    2. Convection: Through fluids (boiling water circulation)

    3. Radiation: Through waves (sunlight heating Earth)

  • Temperature measures the average kinetic energy of particles.

  • Fun Activity: Place your hand above a candle (radiation) or touch a spoon in hot water (conduction).

8. Light

  • Travels in straight lines.

  • Can reflect (bounce) or refract (bend).

  • Examples: Mirrors (reflection), lenses (refraction)

  • Mnemonic: R&R → Reflect & Refract

  • Fun fact: Light is faster than sound — you see lightning before hearing thunder.

  • Visible spectrum: ROYGBIV → Red, Orange, Yellow, Green, Blue, Indigo, Violet

9. Sound

  • Produced by vibrations.

  • Travels in solids (fastest) → liquids → gases (slowest).

  • Properties:

    • Pitch: High/low sound → depends on frequency

    • Volume: Loud/soft → depends on amplitude

  • Example activity: Tap a table and feel vibrations through the solid.

  • Sound needs a medium; it cannot travel in space.

10. Electricity

  • Flow of electrons through a conductor.

  • Components of a circuit:

    • Power source (battery)

    • Wires

    • Load (bulb, motor)

    • Switch (optional)

  • Closed circuit: Works

  • Open circuit: Stops flow

  • Ohm’s Law: V = I × R → Voltage = Current × Resistance

11. Magnetism

  • Magnets have North (N) and South (S) poles.

  • Opposites attract, likes repel.

  • Earth acts as a giant magnet → compasses point north.

  • Applications: Motors, maglev trains, compass navigation

12. Waves

  • Waves transfer energy without moving matter.

  • Types:

    • Transverse: Particles move perpendicular to wave direction (light, water)

    • Longitudinal: Particles move parallel to wave direction (sound)

  • Properties: Wavelength, Frequency, Amplitude

  • Mnemonic: Long waves = low pitch, Short waves = high pitch

13. Simple Machines

  • Make work easier by changing direction or size of force.

  • Types:

    • Lever: Seesaw, crowbar

    • Pulley: Flagpole, cranes

    • Inclined plane (ramp): Load easier to lift

  • Activity: Lift a heavy book using a ruler and eraser as a lever