Physics - Mechanics, Electricity and Waves
Core concepts
GS physics is quantitative. You must handle kinematics and Newtonian dynamics (vectors, free-body diagrams, work–energy theorem, conservation of mechanical momentum and energy), electricity (Coulomb's law, field and potential, capacitors, RC charging/discharging, Ohm's law and circuits) and oscillations and waves (harmonic motion, period–frequency relations, wave speed, refraction, interference). Radioactivity and nuclear equations sometimes appear as a short item.
Traps
- Omitting a force from the free-body diagram (friction, normal reaction, tension) and then misapplying ΣF = ma.
- Sign conventions in energy: gravitational potential energy increases upward, but a chosen axis may point down.
- Confusing field E (a vector, N/C) with potential V (a scalar, volts).
- In RC circuits, mixing the time constant τ = RC with the half-life; the discharge follows exponential decay, not linear.
- Using degrees where radians are required in ω = 2π/T.
Worked example
A block of mass m = 2 kg slides from rest down a frictionless incline of height h = 5 m. Energy conservation: ½mv² = mgh, so v = √(2gh) = √(2·9.8·5) ≈ 9.9 m/s. Note the mass cancels - a frequent distractor. If friction were present, subtract the work of friction W_f = f·d from the mechanical energy before solving. Always state the reference level for potential energy.