SSC JE – General Awareness & Current Affairs
Physics Basics – Study Notes
Audience: Candidates preparing for the SSC Junior Engineer (JE) exam.
Objective: Understand the essential concepts of physics that are frequently asked in the exam, especially in the “General Awareness & Current Affairs” paper.
1. Simple Explanation
Physics is the science of matter, energy, and the interactions between them. It explains how objects move, how forces act, how electricity and magnetism work, and how waves and light behave. In the SSC JE exam, physics is mainly tested through basic principles and their application in everyday situations.
Think of physics as the rule book that tells us what happens when we push, pull, heat, or shine light on something.
2. Key Points
| Area | Key Concept | Representative Formula / Law |
|---|---|---|
| Classical Mechanics | Motion in one dimension | s = ut + ½at² |
| Uniform Circular Motion | v = ωr | |
| Newton’s 1st–3rd Laws | F = ma (2nd law) | |
| Work & Energy | W = F·d; ½mv² | |
| Power | P = W/t = Fv | |
| Electricity & Magnetism | Ohm’s Law | V = IR |
| Kirchhoff’s Laws | ΣI(in) = ΣI(out); ΣV = 0 | |
| Magnetic Force | F = q(v × B) | |
| Faraday’s Law | ε = -dΦ/dt | |
| Waves & Optics | Wave Speed | v = fλ |
| Snell’s Law | n₁ sinθ₁ = n₂ sinθ₂ | |
| Reflection & Refraction | Law of Reflection: θᵢ = θᵣ | |
| Interference | constructive: 2d = mλ | |
| Thermodynamics | First Law | ΔU = Q – W |
| Heat Transfer | Q = mcΔT | |
| Carnot Efficiency | η = 1 – Tₖ/Tₕ | |
| Modern Physics | Photoelectric Effect | K = eV₀ = hf – φ |
| Basic Quantum Idea | E = hf | |
| Relativity (basic) | E = mc² (mass–energy) |
Tip: In SSC JE, you rarely need to derive formulas—just memorize the most common ones above.
3. Worked Example
Problem:
A free‑falling object starts from rest and falls for 3 seconds. What is its velocity and distance travelled?
Solution:
-
Known data
- Initial velocity, (u = 0) m/s
- Acceleration due to gravity, (a = 9.8) m/s²
- Time, (t = 3) s
-
Velocity after time (t)
Use the kinematic equation:
[ v = u + at ] Plugging the values: [ v = 0 + (9.8 \text{ m/s}^2)(3 \text{ s}) = 29.4 \text{ m/s} ] -
Distance travelled
Use:
[ s = ut + \tfrac{1}{2}at^2 ] [ s = (0)(3) + \tfrac{1}{2}(9.8)(3)^2 = 0.5 \times 9.8 \times 9 = 44.1 \text{ m} ]
Answer:
- Final velocity = 29.4 m/s
- Distance travelled = 44.1 m
4. Quick Revision Summary
| Concept | Formula | Units | Note for SSC JE |
|---|---|---|---|
| Linear acceleration | (a = \Delta v / t) | m/s² | Basic, use in kinematics |
| Uniform speed | (v = s/t) | m/s | Simple division |
| Force (Newton 2nd) | (F = ma) | N (kg·m/s²) | Fundamental |
| Work | (W = Fd\cos\theta) | J (N·m) | Cosine term often 1 |
| Power | (P = W/t) or (P = Fv) | W (J/s) | Common in machinery |
| Ohm’s Law | (V = IR) | V, A, Ω | Essential for electrical circuits |
| Resistance in series | (R_{eq} = R_1+R_2+…) | Ω | Additive |
| Resistance in parallel | (1/R_{eq} = 1/R_1+1/R_2+…) | Ω | Reciprocal sum |
| Wave speed | (v = fλ) | m/s | Frequency × wavelength |
| Snell’s Law | (n_1\sinθ_1 = n_2\sinθ_2) | — | Refraction in optics |
| Photoelectric threshold | (hf = φ) | eV | Minimum photon energy |
| Relativistic mass‑energy | (E = mc^2) | J | Basic concept only |
Mnemonic for remembering the first law of thermodynamics:
“Heat in, Work out, Energy change in.”
Final Tips for SSC JE
- Memorize the key formulas and their units.
- Practice at least one problem per concept each week