Physics Fundamentals for Admission
Scope of the paper
Physics questions test conceptual clarity plus simple numerical work. Key areas: units and dimensions, motion in a straight line, Newton's laws, work-energy-power, gravitation, pressure and Archimedes' principle, heat and temperature, waves and sound, light and reflection/refraction, electricity (Ohm's law, series-parallel circuits), and magnetism.
Concepts to understand
Equations of motion (v = u + at, s = ut + ½at², v² = u² + 2as) apply only for uniform acceleration. Newton's second law is a vector relation; the third law pairs act on different bodies, so they never cancel. Work is force times displacement along the force; power is work per unit time. In fluids, buoyancy equals the weight of displaced fluid. In optics, Snell's law (n₁ sin θ₁ = n₂ sin θ₂) and mirror/lens formula (1/f = 1/v + 1/u with sign conventions) are standard. In circuits, series resistances add; parallel conductances add.
Traps to watch
Forgetting unit conversions (cm to m, g to kg); using the wrong sign for g; confusing mass with weight; assuming a body at rest has zero acceleration when forces are balanced; mixing up frequency and wavelength; and applying the lens formula without consistent sign conventions. Dimensional-analysis questions often hide a trap: two quantities with the same dimensions are not necessarily the same physical quantity.
Worked example
A ball is thrown upward at 20 m/s (g = 10 m/s²). Time to reach the top: v = u − gt → 0 = 20 − 10t → t = 2 s. Maximum height: h = u²/(2g) = 400/20 = 20 m. Rule of thumb: at the highest point velocity is zero but acceleration is still g downward.
Practice habit
Draw a quick free-body diagram for every mechanics item before touching formulas.