General Physics Concepts and Scientific Reasoning
General Physics Concepts and Scientific Reasoning tests units, dimensions, Newtonian mechanics, work-energy, gravitation, thermodynamics, waves and the logic of experimental conclusions. It rewards clean reasoning across topics rather than a single formula.
Core rules
- SI base units include metre, kilogram, second, ampere, kelvin, mole and candela. Derived units follow from equations; dimensional formulae help detect wrong expressions.
- Newton's second law F = ma; weight is mg, mass is not weight. Work W = Fd cosθ; kinetic energy ½mv²; gravitational potential energy near Earth mgh.
- Conservation laws are powerful: energy, linear momentum and charge are conserved in isolated systems. In collisions, momentum is conserved even when kinetic energy is not.
- For waves, v = fλ; for a simple pendulum T = 2π√(l/g). Thermodynamic efficiency of a heat engine is η = 1 - T_c/T_h for an ideal reversible engine.
- Scientific reasoning requires a controlled variable, a testable prediction and uncertainty in measurement. A graph should be linearised before using its slope.
Worked example
Check T = 2π√(l/g) dimensionally. [l] = L, [g] = LT⁻², so [l/g] = L/(LT⁻²) = T². The square root gives T, matching the left side. The constant 2π is dimensionless. This does not prove the formula, but a dimensionally wrong formula cannot be correct.
Traps
Treating mass and weight as the same; using v = fλ with frequency in kHz without converting; claiming kinetic energy is always conserved; and accepting a numerical answer without checking units and reasonableness.