NEET Physics — Important Questions & Concepts
Mechanics & Dynamics
Q: A car decelerates from 60 km/h to rest in 5 seconds. Deceleration?
u = 60 km/h = 60 × 1000/3600 = 50/3 m/s ≈ 16.67 m/s
v = 0, t = 5s
a = (v - u)/t = (0 - 16.67)/5 = -3.33 m/s²
Magnitude of deceleration = 3.33 m/s² ≈ 10/3 m/s²
Q: Body at rest on incline angle θ. Condition for equilibrium?
Forces: Normal (N), Weight (mg), Friction (f)
Along incline: f = mg sinθ (friction balances component of weight)
Perpendicular: N = mg cosθ
For equilibrium: f ≤ μN → mg sinθ ≤ μ mg cosθ → tanθ ≤ μ
Max angle of repose: θ_max = arctan(μ)
Fluid Mechanics & Thermal Physics
Q: Blood pressure measured as 120/80 mmHg. What does it mean?
Systolic/Diastolic pressure
120 mmHg systolic = max pressure when heart contracts (systole)
80 mmHg diastolic = min pressure when heart relaxes (diastole)
In SI: 1 mmHg = 133.3 Pa
120 mmHg = 120 × 133.3 = 15,996 Pa ≈ 16 kPa
Bernoulli's principle: P + ½ρv² + ρgh = constant
Higher blood flow velocity → lower pressure (stenosis risk)
Electric & Magnetic Effects
Q: Why is heart's electrical activity monitored with ECG?
Heart muscle generates electrical signals during contraction.
ECG (Electrocardiogram) records potential difference from body surface.
P wave: atrial depolarisation
QRS complex: ventricular depolarisation (strongest signal)
T wave: ventricular repolarisation
Irregular ECG → arrhythmia, heart block, MI diagnosis
Physics: action potential, ionic current, changing electric field
Revision Notes
KINEMATICS: v=u+at | s=ut+½at² | v²=u²+2as
NEWTON'S LAWS: F=ma | Action-Reaction | Inertia
FRICTION: f_s ≤ μ_s N | f_k = μ_k N | tan θ_repose = μ_s
WORK-ENERGY: W=Fs cosθ | KE=½mv² | PE=mgh | Conservation
FLUIDS:
Bernoulli: P + ½ρv² + ρgh = const
Stoke's law: F = 6πηrv
Terminal velocity: v_t = 2r²(ρ-σ)g / 9η
THERMAL:
Q = mcΔT | Q = mL (latent) | Ideal gas: PV = nRT
Specific heat: water = 4200 J/kg·K
OPTICS:
Lens formula: 1/f = 1/v - 1/u
Power P = 1/f (in metres) = D (dioptres)
Eye defects: myopia (concave lens) | hypermetropia (convex lens)
