Physics
TS ECET Physics covers units and dimensions, vectors, kinematics, dynamics, work and energy, rotational motion, gravitation, simple harmonic motion, heat, optics, electrostatics, current electricity, magnetism, electromagnetic induction and semiconductors. The paper rewards unit consistency and correct sign convention more than long derivation.
Core rules
- Dimensional analysis: every valid equation is dimensionally homogeneous; use dimensions to check formulae and convert units.
- Vectors: resolve into perpendicular components; use dot product for work and cross product for torque.
- Kinematics: for uniform acceleration, v = u + at, s = ut + at^2/2, v^2 = u^2 + 2as. Projectile range R = u^2 sin 2θ / g.
- Dynamics: Newton's second law F = ma; friction f = μN; circular motion requires centripetal force mv^2/r.
- Rotation: torque τ = Iα, angular momentum L = Iω; moment of inertia depends on axis.
- SHM: T = 2π sqrt(m/k) for a spring, T = 2π sqrt(l/g) for a simple pendulum.
- Optics: mirror and lens formulae use sign conventions; refraction obeys Snell's law.
- Electricity and magnetism: Ohm's law, Kirchhoff's laws, Coulomb's law, magnetic force F = BIL sinθ, induced emf by Faraday's law.
Worked example
A body is thrown vertically upward with u = 20 m/s. Taking g = 10 m/s^2, maximum height is h = u^2/(2g) = 400/20 = 20 m. Time to reach the top is t = u/g = 2 s; total flight time is 4 s.
Traps
- Mixing cm and m in kinetic energy or force calculations.
- Using peak value instead of RMS in AC power questions.
- Reversing the sign convention in mirrors and lenses.
- Forgetting that g acts downward throughout projectile motion.
- Confusing mass and weight; weight is mg.