General Physics Concepts and Applications
General physics concepts and applications tests mechanics, gravitation, work and energy, momentum, fluids, thermal physics, oscillations, waves, and everyday applications. The exam checks whether you can select the right conservation law and connect a formula to a physical situation.
Core rules and concepts
- Newton laws: net force changes momentum; action-reaction pairs act on different bodies. Equilibrium means zero net force and zero net torque.
- Work-energy theorem: net work equals change in kinetic energy. Mechanical energy is conserved when only conservative forces do work.
- Momentum is conserved when external impulse is negligible; collisions may be elastic or inelastic.
- Gravitational force F = Gm1m2/r^2; near Earth, weight = mg. Orbital speed and escape speed depend on the central mass and radius.
- Pressure in a fluid increases with depth, P = P0 + rho gh. Archimedes buoyancy equals the weight of displaced fluid.
- SHM has acceleration proportional and opposite to displacement; wave speed v = f lambda.
- Thermal energy transfer and ideal-gas relations connect pressure, volume, and temperature.
Worked example
A 1000 kg car accelerates from rest to 20 m/s over 100 m. Change in kinetic energy is 1/2(1000)(20^2) = 2.0 x 10^5 J. If this is the net work, average net force is W/d = 2.0 x 10^5/100 = 2.0 x 10^3 N. This uses the work-energy theorem, not a kinematic guess.
Traps that cost marks
- Confusing mass and weight.
- Using momentum conservation when a large external force acts.
- Forgetting that work is zero when force is perpendicular to displacement.
- Mixing gauge pressure and absolute pressure.
- Using degrees or wrong units in wave and SHM formulas.