Physics: Mechanics to Modern Physics
Physics on SITEEE tests mechanics, electrostatics, current electricity, optics, thermodynamics, and modern physics at the Class 11–12 level. Expect numericals that combine two ideas rather than single-formula recall. The paper is computer-based, so unit checks and quick estimation help.
Core rules and concepts
- Newton's second law: F_net = ma. Resolve forces along chosen axes and include friction f = μN.
- Work–energy theorem: W_net = ΔK. A conservative force can be represented by potential energy.
- Electrostatics: E = kQ/r^2, V = kQ/r; field lines run from positive to negative and are perpendicular to equipotentials.
- Circuits: V = IR; series shares current, parallel shares voltage; power P = I^2R = V^2/R.
- Optics: n1 sin θ1 = n2 sin θ2; lens formula 1/f = 1/v - 1/u with a consistent sign convention.
Worked example
A 2 kg block starts from rest and slides 5 m down a 30° rough incline with μ = 0.25. Using g = 10 m/s^2, find its speed at the bottom. Height fallen: h = 5 sin 30° = 2.5 m, so initial potential energy mgh = 2(10)(2.5) = 50 J. Friction f = μmg cos 30° = 0.25(2)(10)(0.866) = 4.33 N; friction work = 4.33(5) = 21.65 J. Thus kinetic energy = 50 - 21.65 = 28.35 J. Since K = 1/2 mv^2, v = sqrt(2K/m) = sqrt(28.35) = 5.3 m/s.
Traps
Using the 5 m slope distance as height; adding friction work with the wrong sign; mixing mirror and lens sign conventions; treating friction as a potential-energy term.