Physics Basics – Study Notes
(For General Awareness & Current Affairs – Chhattisgarh PSC)
1. Simple Explanation
Physics is the science of matter, energy, space, and time.
It seeks to describe how the universe behaves, from the tiniest particles to the largest cosmic structures, using laws that are expressed mathematically.
Key Idea:
Every physical phenomenon can be explained by a set of fundamental principles (laws) that apply universally.
2. Core Concepts & Key Points
| Concept | What It Is | Why It Matters | Typical Formulas |
|---|---|---|---|
| Newton’s Laws of Motion | 1) Inertia, 2) F = ma, 3) Action–Reaction | Foundation of classical mechanics | (F = ma) |
| Kinematics | Motion without forces | Predicts position, velocity, acceleration | (s = ut + \frac{1}{2}at^2) |
| Energy | Kinetic (KE) & Potential (PE) | Conservation of energy explains many processes | (KE = \frac{1}{2}mv^2), (PE = mgh) |
| Work & Power | Work = Force × Distance, Power = Work/time | Technology & energy efficiency | (W = Fd), (P = \frac{W}{t}) |
| Thermodynamics | Heat, temperature, 3 Laws | Drives engines, climate, biology | ( \Delta U = Q - W) |
| Electricity & Magnetism | Charges, currents, magnetic fields | Power generation, electronics | (V = IR), (F = qvB) |
| Waves & Optics | Wave properties, light behavior | Telecommunications, optics | (c = \lambda f) |
| Modern Physics | Quantum theory, relativity, nuclear physics | Nuclear power, GPS, particle physics | (E = mc^2), (E = hf) |
3. Worked Example
Problem
A 5 kg block slides down a 30° frictionless incline from a height of 4 m. Calculate its speed at the bottom and the kinetic energy just before it reaches the ground.
Step‑by‑Step Solution
| Step | Explanation | Calculation |
|---|---|---|
| 1. Find potential energy at the top | (PE = mgh) | (PE = 5 \times 9.8 \times 4 = 196\ \text{J}) |
| 2. Assume no losses | Energy is conserved (no friction) | – |
| 3. Set PE = KE at bottom | (KE_{\text{bottom}} = PE_{\text{top}}) | (KE = 196\ \text{J}) |
| 4. Relate KE to speed | (KE = \frac{1}{2}mv^2) | (196 = \frac{1}{2} \times 5 \times v^2) |
| 5. Solve for (v) | (v^2 = \frac{392}{5} = 78.4) | (v = \sqrt{78.4} \approx 8.85\ \text{m/s}) |
Answer:
- Speed at bottom ≈ 8.85 m/s
- Kinetic energy just before reaching the ground = 196 J
4. Quick Revision Summary
| Topic | Key Formula | Important Note |
|---|---|---|
| Newton’s 2nd Law | (F = ma) | Force = mass × acceleration |
| Kinematic Equation | (s = ut + \frac{1}{2}at^2) | Works for constant acceleration |
| Kinetic Energy | (KE = \frac{1}{2}mv^2) | Energy of motion |
| Potential Energy (gravity) | (PE = mgh) | Height above reference |
| Work | (W = Fd) | Positive if force & displacement align |
| Power | (P = \frac{W}{t}) | Energy per unit time |
| Ohm’s Law | (V = IR) | Voltage, current, resistance |
| Speed of Light | (c = \lambda f) | Fundamental constant |
| Einstein’s Mass–Energy | (E = mc^2) | Mass‑energy equivalence |
Quick Tips for PSC Exam
- Remember Units – SI units (kg, m, s, J, W, V, A, Ω).
- Use Conservation Laws – Energy, momentum, charge.
- Know Current Affairs –
- Renewable Energy: Solar PV efficiency rising > 25% in 2025.
- Nuclear Power: India’s 1.7 GW of nuclear capacity, with new 800 MW units planned.
- Quantum Computing: Indian Institute of Science (IISc) announced a 20‑qubit chip in 2024.
- Practice Simple Calculations – Speed, acceleration, power, Ohm’s law.
- Read Recent Scientific News – Helps with “Current Affairs” part of General Awareness.
Final Thought
Physics isn’t just equations