Physics Study MYP 4-5

Unit 1: Forces and Moments

Key Concepts:

  • Forces: Contact (friction, tension) and non-contact (gravity, magnetism).

  • Newton’s Laws:

    • 1st Law (Inertia): Objects stay at rest or move at constant velocity unless acted upon.

    • 2nd Law (F = ma): Force equals mass times acceleration.

    • 3rd Law (Action-Reaction): Every force has an equal and opposite reaction.

  • Resultant Force: Net force determines motion (balanced = no acceleration; unbalanced = acceleration).

  • Moments: Turning effect of a force around a pivot (Moment = Force × Distance).

  • Equilibrium: Sum of clockwise moments = sum of anticlockwise moments.

Practice Questions:

  1. A 6 kg object accelerates at 4 m/s². Calculate the force.
    Answer: F=ma=6×4=24 NF=ma=6×4=24N.

  2. A 50 N force is applied 0.5 m from a pivot. Calculate the moment.
    Answer: Moment = 50×0.5=25 Nm50×0.5=25Nm.

  3. Explain why a book on a table doesn’t move (use Newton’s 1st Law).

Revision Tips:

  • Draw free-body diagrams for forces.

  • Use the principle of moments to solve seesaw problems.

Unit 2: Energy and Resources

Key Concepts:

  • Energy Types: Kinetic, thermal, chemical, gravitational potential, etc.

  • Energy Transfers: Mechanical, electrical, heating, radiation (Sankey diagrams show efficiency).

  • Renewable vs. Non-Renewable:

    • Renewable: Solar, wind, hydro (sustainable but intermittent).

    • Non-Renewable: Coal, oil, nuclear (high output but polluting).

Practice Questions:

  1. Name three energy stores and give an example of each.
    Answer: Kinetic (moving car), thermal (hot stove), chemical (battery).

  2. Why is energy never 100% efficient in transfers?
    Answer: Some energy is always lost as heat (e.g., friction).

  3. Compare solar and nuclear energy (one pro and con each).

Revision Tips:

  • Practice drawing Sankey diagrams (e.g., for a light bulb: 10% light, 90% heat).

  • Debate pros/cons of energy sources.

Unit 3: Radioactivity and Nuclear Physics

Key Concepts:

  • Radiation Types:

    • Alpha (α): Helium nucleus (stopped by paper).

    • Beta (β): High-speed electron (stopped by aluminum).

    • Gamma (γ): EM wave (stopped by lead).

  • Half-Life: Time for half of nuclei to decay (used in carbon dating).

  • Nuclear Fission: Splitting uranium nuclei to release energy (used in power plants).

  • Risks/Benefits: Low CO₂ but radioactive waste.

Practice Questions:

  1. Which radiation is most penetrating?
    Answer: Gamma.

  2. A sample’s activity halves in 5 years. What’s its half-life?
    Answer: 5 years.

  3. Explain one risk of nuclear power.
    Answer: Radioactive waste harms health/environment.

Revision Tips:

  • Use decay graphs to calculate half-life.

  • Research Chernobyl/Fukushima case studies.

Unit 4: Waves and EM Spectrum

Key Concepts:

  • Wave Properties: Wavelength (λ), frequency (f), speed (v = fλ).

  • Wave Types:

    • Transverse: Light (vibrations perpendicular to direction).

    • Longitudinal: Sound (vibrations parallel to direction).

  • Wave Behaviors: Reflection, refraction, absorption.

  • EM Spectrum: Radio → Gamma (long λ = low energy; short λ = high energy).

Practice Questions:

  1. A wave has f = 10 Hz and λ = 2 m. Calculate speed.
    Answer: v=fλ=10×2=20 m/sv=fλ=10×2=20m/s.

  2. Why does light bend in glass?
    Answer: Refraction (slows down in denser medium).

  3. Give two uses of microwaves.
    Answer: Cooking, mobile phones.

Revision Tips:

  • Label wave diagrams (crest, trough, amplitude).

  • Memorize EM spectrum order (e.g., "Rabbits Mate In Very Unusual eXpensive Gardens"