Physics basics: General Awareness & Current Affairs Notes for Andhra Pradesh PSC

Physics Basics – Andhra Pradesh PSC

(General Awareness & Current Affairs – Physics)

Why study Physics?
Physics is the science that explains how the universe works – from the motion of everyday objects to the behaviour of sub‑atomic particles. For civil‑services exams, a solid grasp of basic physics concepts helps you understand natural phenomena, evaluate scientific reports, and answer analytical questions in Current Affairs.

1. Simple Explanation

Concept	What it means in plain language
Physics	The study of matter, energy, and the fundamental forces that govern their interactions.
Matter	Anything that occupies space and has mass (e.g., a rock, water, air).
Energy	The capacity to do work – can be kinetic (motion), potential (position), thermal, etc.
Force	A push or pull that changes an object's motion or shape.
Work	Energy transferred by a force acting over a distance.
Power	Rate at which work is done or energy is transferred.

2. Key Points – Core Topics Covered

Topic	Core Ideas	Typical PSC Questions
Kinematics	• Displacement, velocity, acceleration • Uniformly Accelerated Motion (UAM) • Projectile motion	“A ball is dropped from a 50 m height. How long does it take to hit the ground?”
Newton’s Laws of Motion	1️⃣ First – Inertia 2️⃣ Second – (F = ma) 3️⃣ Third – Action–Reaction	“Explain why a passenger seatbelt is important in a car accident.”
Work, Energy & Power	• Work (W = F \times d \times \cos\theta) • Kinetic Energy (KE = \tfrac12 mv^2) • Potential Energy (PE = mgh) • Power (P = \frac{W}{t})	“Calculate the power output of a 5 kW electric motor.”
Conservation Laws	• Conservation of Energy • Conservation of Momentum	“What happens to the momentum of a ball after it collides elastically with another ball?”
Simple Harmonic Motion (SHM)	• Pendulum period (T = 2\pi\sqrt{\frac{L}{g}}) • Spring oscillation (T = 2\pi\sqrt{\frac{m}{k}})	“Find the period of a 2 m long pendulum.”
Electricity & Magnetism (Basic)	• Ohm’s Law (V = IR) • Basic circuit concepts (series, parallel)	“A resistor of 5 Ω is connected to a 12 V source. What is the current?”
Light & Wave	• Reflection, Refraction • Doppler Effect	“Explain why the sky appears blue.”

Tip: For PSC, focus on conceptual understanding rather than memorising long formulas. The exam often tests your ability to apply ideas to everyday scenarios.

3. Worked Example

Problem (Common PSC type):
A 2 kg block slides on a horizontal table with a coefficient of kinetic friction (\mu_k = 0.2). It is pushed with a constant horizontal force of 10 N. Find the acceleration of the block.

Step‑by‑Step Solution

Identify forces
- Applied force (F_a = 10\ \text{N}) (horizontal)
- Friction force (F_f = \mu_k N)
- Normal force (N = mg = 2 \times 9.8 = 19.6\ \text{N})
Compute friction
[ F_f = 0.2 \times 19.6 = 3.92\ \text{N} ]
Net horizontal force
[ F_{\text{net}} = F_a - F_f = 10 - 3.92 = 6.08\ \text{N} ]
Use Newton’s second law
[ a = \frac{F_{\text{net}}}{m} = \frac{6.08}{2} = 3.04\ \text{m/s}^2 ]

Answer: The block accelerates at (3.04\ \text{m/s}^2).

Quick Check:
• If friction were zero, the block would accelerate at (5\ \text{m/s}^2).
• The friction force reduced the net force by about (4\ \text{N}), which matches the calculation.

4. Quick Revision Summary

Concept	Formula / Rule	Example Use
Velocity	(v = \frac{s}{t})	“Speed of a car after 10 s.”
Acceleration	(a = \frac{v_f - v_i}{t})	“Change in speed from 0 to 20 m/s in 5 s.”
Newton‑2	(F = ma)	“Force needed to accelerate 5 kg mass at 2 m/s².”
Work	(W = Fd\cos\theta)	“Work done lifting a 10 kg weight 2 m high.”
Energy	(KE = \tfrac12 mv^2), (PE = mgh)	“Total energy of a 3 kg mass at 10 m height.”
Power	(P = \frac{W}{t})	“Power output of a 250