Physics (Mechanics, Electricity, Heat)
Syllabus Unit: General Ability Test (GAT)
Why it matters
Chapter overview
The Physics component of the GAT covers classical mechanics (Newton's laws, work-energy), heat and thermodynamics, electricity and magnetism (Ohm's law, circuits, electromagnetic induction), and light, sound and modern physics — largely at the Class XI-XII NCERT level, testing formula recall and conceptual clarity on everyday physical phenomena.
Mathematics & General Ability General Ability Test (GAT) 60% weightage
Live Animation1 / 4
1Apply the net forceAn unbalanced force acts on the body
2F = ma gives accelerationAcceleration is directly proportional to net force
3Velocity changes over timev = u + at, from constant acceleration
4Work done changes kinetic energyW = ΔKE, the work-energy theorem
1Laws of Motion & Work-Energy
Newton's three laws explain why objects move the way they do, and the work-energy theorem links the force applied to the energy an object gains.
Learning Objectives
- State Newton's three laws of motion and identify real examples of each.
- Apply F=ma to compute force, mass or acceleration in numerical problems.
- Distinguish work, kinetic energy and potential energy, and apply the work-energy theorem.
- State the law of conservation of energy and conservation of momentum.
Key Terms
Newton's Second LawF = ma; the net force on a body equals mass times acceleration, in the direction of the force.
InertiaA body's tendency to resist a change in its state of motion (Newton's First Law); mass is the measure of inertia.
Work-Energy TheoremThe work done by the net force on a body equals its change in kinetic energy, W = ΔKE.
Conservation of MomentumIn the absence of external force, the total momentum of a system before and after a collision stays constant.
Newton's three laws together describe every everyday motion — from why a seated passenger lurches forward when a bus brakes, to how a rocket accelerates by expelling exhaust.
Newton's three laws
- First Law (Inertia) — a body stays at rest or in uniform motion unless acted on by a net external force.
- Second Law — F=ma, the net force equals the rate of change of momentum.
- Third Law — for every action there is an equal and opposite reaction.
Common MistakeAction-reaction pairs act on two DIFFERENT bodies, so they never cancel each other out on the same object.
Work, energy and power
Work W = F·d·cosθ; KE = ½mv²; PE = mgh; Power P = W/t
Work-energy theorem
W(net) = ΔKE = ½mv² − ½mu²
Conservation laws
- Energy — total mechanical energy (KE+PE) is conserved when only conservative forces act.
- Momentum — total momentum before equals total momentum after, for an isolated system such as a collision.
Exam TipIn collision problems, always check momentum first — it's conserved in both elastic and inelastic collisions, unlike kinetic energy.