Physics Basics – NABARD Grade‑A (General Awareness & Current Affairs)
Why Physics?
In NABARD examinations a solid grasp of basic physics helps you:
- Understand the science behind emerging technologies (e.g., renewable energy, green transport).
- Answer questions on “Technology & Innovation” and “Science & Technology” sections.
- Build analytical thinking – a skill highly valued by NABARD.
1. Simple Explanation of Core Concepts
| Concept | What it is | Everyday Analogy |
|---|---|---|
| Newton’s Laws | Rules that describe motion of objects. | A car that starts moving only when the engine pushes (1st law), acceleration proportional to force (2nd), equal and opposite forces (3rd). |
| Work, Energy & Power | Work = force × distance. Energy = capacity to do work. Power = rate of doing work. | Lifting a box (work), battery capacity (energy), a power‑tool rating (power). |
| Conservation of Energy | Total energy in a closed system stays constant; only changes form. | A pendulum swings, kinetic ↔ potential. |
| Simple Harmonic Motion (SHM) | Oscillatory motion where a restoring force is proportional to displacement. | A spring-loaded toy car oscillating back and forth. |
| Electric Circuits | Flow of electrons through conductors, governed by voltage, current, resistance. | Water flowing through pipes: voltage = pressure, current = flow rate, resistance = pipe size. |
| Magnetism | Force between moving charges or magnetic materials. | Compass needle aligning with Earth’s magnetic field. |
| Thermodynamics | Study of heat, work, energy transfer; laws governing energy in systems. | A refrigerator extracts heat from inside to keep it cold. |
2. Key Points
2.1 Newton’s Laws
| Law | Formula | Key Takeaways |
|---|---|---|
| 1st | Fₛ = 0 → v = constant | Inertia keeps objects at rest or in uniform motion. |
| 2nd | F = m·a | Force applied → acceleration. Mass is resistance to acceleration. |
| 3rd | F₁₂ = –F₂₁ | Action and reaction forces act on different bodies. |
2.2 Work, Energy & Power
| Concept | Formula | Units |
|---|---|---|
| Work | W = F·d·cosθ | Joule (J) |
| Kinetic Energy | KE = ½ m v² | J |
| Potential Energy (gravity) | PE = m g h | J |
| Power | P = W/t | Watt (W) |
2.3 Conservation of Energy
- Total Energy (E) = KE + PE (for mechanical systems).
- In absence of non‑conservative forces: E_initial = E_final.
2.4 Simple Harmonic Motion
| Parameter | Formula | Notes |
|---|---|---|
| Displacement | x(t) = A cos(ωt + φ) | A = amplitude, ω = angular frequency, φ = phase. |
| Period | T = 2π/ω | Time for one full oscillation. |
| Frequency | f = 1/T | Oscillations per second (Hz). |
| Energy in SHM | E = ½ k A² (spring) | Constant for conservative forces. |
2.5 Electric Circuits
| Symbol | Meaning | SI Unit |
|---|---|---|
| V | Voltage | Volt (V) |
| I | Current | Ampere (A) |
| R | Resistance | Ohm (Ω) |
| P | Power | Watt (W) |
| C | Capacitance | Farad (F) |
| L | Inductance | Henry (H) |
- Ohm’s Law: V = I·R
- Power in circuits: P = V·I = I²R = V²/R
2.6 Magnetism
- Magnetic Force: F = q(v × B) (Lorentz force).
- Magnetic Field of a Solenoid: B = μ₀ n I
- μ₀ = permeability of free space (4π × 10⁻⁷ T·m/A).
- n = turns per meter, I = current.
2.7 Thermodynamics
| Law | Essence |
|---|---|
| 1st | Energy cannot be created or destroyed. |
| 2nd | Entropy of an isolated system never decreases. |
| 3rd | At absolute zero, entropy approaches a constant minimum. |
- Heat Transfer: conduction, convection, radiation.
3. Worked Example
Problem:
A 12 kg crate is pulled along a horizontal floor with a constant force of 60 N. The floor is rough, causing a kinetic friction force of 20 N opposing the motion.
- Find the acceleration of the crate.
- **Calculate