Karnataka Police Constable – General Awareness & Current Affairs
Physics Basics
Why this is important
The Karnataka Police Constable (KPC) exam tests basic scientific knowledge. Topics from physics give you a solid foundation for answering questions on mechanics, energy, waves, and electricity—common in the General Awareness and Current Affairs sections.
Simple Explanation
Physics is the study of matter, energy, and the interactions between them.
- Mechanics deals with motion and forces.
- Energy and work quantify the capacity to do work.
- Thermodynamics deals with heat and temperature.
- Waves & Optics explain light, sound, and electromagnetic phenomena.
- Electromagnetism underpins electricity, magnetism, and circuits.
A clear grasp of these fundamentals helps you solve real‑world problems and answer exam questions reliably.
Key Points
| Concept | Main Idea | Formula (if any) | Typical Exam Question |
|---|---|---|---|
| Units | SI system: metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), candela (cd). | – | “What is the SI unit of force?” |
| Newton’s Laws | 1️⃣ Inertia, 2️⃣ F = ma, 3️⃣ Action‑reaction. | 1. F = m × a | “A 10 kg mass is pulled with 30 N; find acceleration.” |
| Kinematics | Motion description: displacement, velocity, acceleration. | v = u + at; s = ut + ½at² | “A car accelerates uniformly from 0 to 20 m/s in 10 s.” |
| Work & Energy | Work = force × displacement; kinetic/potential energy. | W = F × s; K = ½ m v²; U = mgh | “Work done lifting a 5 kg box 2 m high.” |
| Power | Rate of doing work. | P = W / t | “An electric bulb uses 60 W; how much energy in 5 h?” |
| Conservation Laws | Energy & momentum are conserved in isolated systems. | – | “Two carts collide; find final velocities.” |
| Thermodynamics | Heat (Q), Temperature (T), First law: ΔU = Q – W. | ΔU = Q – W | “Heat 500 J is supplied to a gas; its internal energy increases by 300 J.” |
| Waves | Frequency (f), wavelength (λ), speed (c = λ × f). | – | “Sound travels 340 m/s; frequency 200 Hz; find wavelength.” |
| Basic Optics | Reflection, refraction, lenses, mirrors. | Snell’s law: n₁ sinθ₁ = n₂ sinθ₂ | “Light refracts from air to water at 30°; find refracted angle.” |
| Electromagnetism | Ohm’s law, Kirchhoff’s laws, magnetic field (B). | V = IR; B = μ₀ I / (2πr) | “Resistor of 10 Ω receives 5 V; find current.” |
Worked Example
Problem (common in KPC exam):
A 40 kg police baton is thrown horizontally with an initial speed of 8 m/s. Neglect air resistance. What is the horizontal distance it covers before hitting the ground if the height of the throw is 1.5 m?
Solution:
-
Time of flight – determined only by vertical motion.
[ y = \frac{1}{2}gt^2 \quad\text{(with } y = 1.5,\text{m, } g = 9.8,\text{m/s}^2) ] Solve for t: [ t = \sqrt{\frac{2y}{g}} = \sqrt{\frac{2 \times 1.5}{9.8}} \approx \sqrt{0.306} \approx 0.553,\text{s} ] -
Horizontal distance (range) – constant horizontal velocity vₓ = 8 m/s.
[ x = vₓ \times t = 8 \times 0.553 \approx 4.42,\text{m} ]
Answer: The baton travels about 4.4 m horizontally before striking the ground.
Quick Revision Summary
- Units: m, kg, s, N, J, W, °C, etc.
- Newton’s 2nd Law: F = m × a.
- Work: W = F × s (J).
- Kinetic Energy: K = ½ m v².
- Potential Energy: U = mgh.
- Power: P = W / t (W).
- Energy Conservation: ΔU = Q – W.
- Wave Speed: c = λ × f.
- Snell’s Law: n₁ sinθ₁ = n₂ sinθ₂.
- Ohm’s Law: V = IR.
Quick Flashcards
| Question | Answer |
|---|---|
| SI unit of force? | Newton (N) |
| Formula for kinetic energy? | ½ m v² |
| Power of |