Velocity time graphs acceleration

Physics: Core Concepts, Laws, and Problem-Solving Techniques

Physics is the most fundamental of the natural sciences. It seeks to understand the basic laws that govern the universe, from subatomic particles to galaxies. This chapter covers important physics concepts and problem-solving strategies for CBSE examinations. Physics problems require a systematic approach: identifying known and unknown quantities, selecting the appropriate principle or equation, solving algebraically before substituting numerical values, and checking for dimensional consistency and reasonableness.

Key concepts: kinematics (displacement, velocity, acceleration, equations of motion), dynamics (Newton's three laws — inertia, F=ma, action-reaction), work-energy (work-energy theorem, conservation of mechanical energy), rotational motion (torque, moment of inertia, angular momentum), gravitation (universal law, Kepler's laws, escape velocity), properties of matter (elasticity, stress/strain, pressure), thermodynamics (laws, heat transfer, specific heat), waves and oscillations (SHM, wave equation, superposition, Doppler effect), and optics (reflection, refraction, lenses).

Systematic problem-solving: (1) Read carefully; identify known/unknown. (2) Draw a diagram or free-body diagram showing all forces. (3) Select the appropriate physical law. (4) Solve algebraically first. (5) Substitute values with correct units. (6) Check dimensional consistency and whether the answer is reasonable. Free-body diagrams are essential — draw all force vectors on each object, apply F=ma along each independent direction.

Conservation laws are powerful tools: conservation of energy (KE+PE=constant), conservation of linear momentum (p=constant when no external force), conservation of angular momentum (L=constant when no external torque). The SI system (m, kg, s, A, K, mol, cd) standardises measurements. Significant figures indicate precision. Dimensional analysis checks equation consistency.

• Systematic approach: identify known/unknown, draw diagrams, select law, solve algebraically, substitute with units, check reasonableness.
• Newton's laws: inertia (F=0 -> constant v), F=dp/dt=ma, action-reaction (on different bodies). Free-body diagrams for force analysis.
• Energy: KE=0.5mv2, PE=mgh (gravitational), PE=0.5kx2 (spring). Work-energy: W=deltaKE. Conservation: KE+PE=constant.
• SI units: m, kg, s, A, K, mol, cd. Dimensional analysis: each term in equation must have same dimensions.
• Conservation: energy (isolated system), linear momentum (no external F), angular momentum (no external torque).