NEET Exam Strategy — Work, Energy & Power — Summary | NoteTube

Identify all forces first: Before applying the work-energy theorem, list every force acting: applied force, gravity, normal, friction, spring. Work by normal and centripetal forces is zero.
String vs rod — read carefully: The problem will specify "string", "rod", "wire", or "inextensible string". Rod → v_top(min) = 0; String → v_top(min) = √(gR). This distinction has appeared as a direct MCQ.
Collision type — look for key words: "Sticks together" or "move together after" → perfectly inelastic. "Elastic collision" → KE conserved. "Coefficient of restitution = 1" → elastic. No qualifier? Assume elastic unless told otherwise.
Use KE = $p^{2}$ /(2m) when momenta are equal: Problems comparing KE of two bodies with the same momentum: heavier body has less KE. Use $p^{2}$ /(2m), not ½ $mv^{2}$ .
Energy conservation shortcut: For height problems (projectile, vertical circle), energy conservation gives speed at any height directly without kinematics. This is faster than using $v^{2}$ = $u^{2}$ + 2as.
Power problems — find terminal speed: At terminal (maximum) speed, acceleration = 0 → driving force = total resistance. Then P = F_resistance × v_max.
Check dimensions quickly: Work, KE, PE all share [ $M^{1}$$L^{2}$$T^{-2}$ ]. Power is [ $M^{1}$$L^{2}$$T^{-3}$ ]. A dimensional check in 5 seconds catches many formula errors.
For rough incline problems: Normal force N = mg cos θ (not mg). Friction = μN = μmg cos θ. Gravity component along incline = mg sin θ. Set up force balance or energy equation carefully.
Multi-step collision problems: When a collision is followed by motion on a surface (e.g., ballistic pendulum), split into two steps: (1) momentum conservation during collision, (2) energy conservation during subsequent motion.
Avoid over-using √(5gR): √(5gR) is the minimum bottom speed for a STRING, not a rod, not a bead on a wire. Confirm the constraint before applying.