UPSSSC PET · Bite-size lessons
Basic Physics
About 6 min · General Science · English
Time worked out from the lesson's 341 words at 150 words a minute, plus a minute for each question.
This topic tests your understanding of fundamental physical principles that govern everyday phenomena—from why objects fall to how electricity flows through circuits.
Key ideas
- Motion is change in position over time; velocity includes direction (vector) while speed does not (scalar). Acceleration is the rate of change of velocity.
- Newton's Laws govern force and motion: (1) objects resist change in motion (inertia), (2) force equals mass times acceleration (F = ma), (3) every action has an equal and opposite reaction.
- Gravitation is the universal attractive force between masses; weight is gravitational force on an object (W = mg), while mass remains constant everywhere.
- Work is done when force causes displacement in its direction; energy is the capacity to do work. Both are measured in joules. Energy transforms but total energy remains conserved.
- Heat is thermal energy transfer from hot to cold bodies; temperature measures hotness. Heat flows via conduction (direct contact), convection (fluid movement), and radiation (electromagnetic waves).
Quick reference
- SI Units: Force (newton), Work/Energy (joule), Power (watt), Charge (coulomb), Current (ampere), Resistance (ohm)
- g = 9.8 m/s² (often approximated as 10 m/s² for quick calculations)
- Speed of light = 3 × 10⁸ m/s; speed of sound in air ≈ 340 m/s
- 1 kWh = 1 unit of electricity = 3.6 million joules
- Ohm's Law: V = IR; higher resistance means lower current for same voltage
Check yourself: 3 questions
1. A car accelerates uniformly from rest and reaches a velocity of 20 m/s in 5 seconds. What is the acceleration of the car?
2. A force of 50 N is applied on a body of mass 10 kg. If the body starts from rest on a frictionless surface, what distance will it cover in 4 seconds?
3. An electric heater of resistance 20 ohms is connected to a 220 V supply for 2 hours. If the cost of electricity is Rs 5 per unit (1 unit = 1 kWh), what is the total cost of using the heater?
This lesson is cut from the topic's note, not rewritten. Fact-checked on 17 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.
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