Physics Basics – Study Notes for SBI PO (General Awareness & Current Affairs)
Why this matters?
The SBI PO exam tests general awareness and current affairs. A solid grasp of Physics Basics helps in:
- Understanding news on energy, environment, space, and technology.
- Answering “technology & innovation” type questions.
- Building confidence in quantitative reasoning sections.
1. Simple Explanation
Physics is the science that studies matter, energy, motion, and forces. For the SBI PO syllabus, you only need to know the fundamental concepts and basic formulas that frequently appear in news stories – such as energy conservation, electricity, thermodynamics, and mechanics. Think of it as a toolbox: each concept is a tool you can use to solve everyday problems.
2. Key Points (Bullet‑style)
| Concept | Definition | Key Formula(s) | Typical Exam Question |
|---|---|---|---|
| Units & SI System | Standard measurement units (m, kg, s, A, K, mol, cd). | — | “A device uses 100 W of power.” |
| Speed, Velocity, Acceleration | Speed = distance/time; Velocity = displacement/time; Acceleration = change in velocity/time. | (v = \frac{s}{t}) (a = \frac{\Delta v}{t}) |
“A car accelerates from 0 to 20 m/s in 10 s.” |
| Newton’s 3 Laws | 1. Inertia 2. Force = mass × acceleration 3. Action‑reaction. | (F = ma) | “Why does a passenger lurch forward when a bus stops suddenly?” |
| Work & Energy | Work = force × displacement; Kinetic Energy (KE) = (½mv^2); Potential Energy (PE) = (mgh). | (W = F \cdot d \cdot \cos\theta) (KE = \frac{1}{2}mv^2) (PE = mgh) |
“What is the work done by a 10 N force moving 5 m?” |
| Power | Rate of doing work. | (P = \frac{W}{t}) | “A 200 W bulb consumes how many joules in 30 s?” |
| Gravity & Weight | Gravitational force between masses; Weight = mass × (g). | (F_g = G\frac{m_1m_2}{r^2}) (W = mg) |
“What is the weight of a 70 kg person on the Moon?” |
| Torque & Lever | Rotational analog of force. | (\tau = rF\sin\theta) | “How much torque does a 5‑kg wrench apply at 0.3 m?” |
| Simple Harmonic Motion (SHM) | Oscillatory motion with restoring force ∝ displacement. | (x(t) = A\cos(\omega t + \phi)) (\omega = 2\pi f) |
“Period of a 0.5 kg mass on a 200 N/m spring.” |
| Electric Current & Resistance | Flow of charge; opposition to flow. | (I = \frac{Q}{t}) (V = IR) |
“Find resistance if 5 A flows at 12 V.” |
| Capacitance | Ability to store charge. | (C = \frac{Q}{V}) | “Capacitance of a parallel‑plate capacitor with area 0.04 m², separation 0.01 m, dielectric ε₀.” |
| Thermodynamics | Energy transfer via heat & work. | First law: (\Delta U = Q - W) | “Heat added to a gas raises its temperature by 5 K.” |
| Wave & Light | Oscillation, frequency, wavelength. | (v = f\lambda) | “Speed of light in water (n=1.33).” |
| Magnetism | Magnetic field, force on moving charges. | (F = qvB\sin\theta) | “A 2‑C charge moves at 3 m/s in 0.5 T field.” |
3. Worked Example
Problem (Speed, Acceleration & Work)
A train of mass 4 × 10⁵ kg starts from rest and accelerates uniformly to 25 m/s in 200 s.
(a) What is the train’s acceleration?
(b) What is the net force acting on the train?
(c) How much work is done by this force?
(a) Acceleration
(a = \frac{\Delta v}{t} = \frac{25 - 0}{200} = 0.125\ \text{m/s}^2)
(b) Net Force
(F = ma = (4 \times 10^5\ \text{kg}) \times 0.125\ \text{m/s}^2 = 5.0 \times 10^4\ \text{N})
(c) Work Done
Displacement (s = \frac{1}{2}at^2 = \frac{1}{2} \times 0.125 \times (200)^2 = 2500\ \text{m})
(W = Fs = (5.0 \times 10^4\ \text{N}) \times (2500\ \text{m}) = 1.25 \times 10^8\ \text{J})
Answer
- Acceleration = 0.125 m/s²
- Net force = 5.0 × 10⁴ N
- Work done = 1.25 × 10⁸ J
4. Quick Revision Summary
| Topic | Take‑away |
|---|---|
| Units | SI system is the standard. |
| **Speed |