UPSC CSE Prelims
Physics and Applied Technology Previous Year Questions (PYQs)
Showing solved Previous Year Questions for Chapter: Physics and Applied Technology
Topic Breakdown: Scroll →
Ball bearings are used in bicycles, cars, etc., because
Detailed Explanation:
Ball bearings reduce the effective area of contact between the wheel and axle, replacing sliding friction with rolling friction.
Reduced contact area means lower friction and higher efficiency, as rolling balls have a much lower coefficient of friction than flat surfaces sliding against each other.
Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena are responsible for this?
- Dispersion
- Refraction
- Internal reflection
Select the correct Solution using the codes given below.
Detailed Explanation:
Refraction occurs when sunlight enters and exits the raindrop, bending light at air-water boundaries.
Dispersion separates white light into constituent colours as different wavelengths refract at different angles inside the droplet.
Internal reflection bounces the dispersed light off the rear inner surface of the raindrop back toward the observer, creating the visible rainbow arc.
All three phenomena—Dispersion, Refraction, and Internal Reflection—work together to form a rainbow.
The known forces of nature can be divided into four classes, viz, gravity, electromagnetism, weak nuclear force and strong nuclear force. With reference to them, which one of the following statements is not correct?
Detailed Explanation:
❌ Statement 1 – Incorrect: Gravity is the weakest of the four fundamental forces, not the strongest.
✅ Statement 2 – Correct: Electromagnetism acts only on particles with electric charge (positive or negative).
✅ Statement 3 – Correct: Weak nuclear force is responsible for radioactivity and beta decay.
✅ Statement 4 – Correct: Strong nuclear force holds protons and neutrons together inside the atomic nucleus.
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Consider the following statements - If there were no phenomenon of capillarity
- It would be difficult to use a kerosene lamp
- One would not be able to use a straw to consume a soft drink
- The blotting paper would fail to function
- The big trees that we see around would not have grown on the earth
Detailed Explanation:
✅ Statement 1 – Correct: Kerosene lamps rely on capillary action to draw kerosene up the wick from the reservoir for combustion.
❌ Statement 2 – Incorrect: Drinking through a straw works by air pressure difference, not capillarity; sucking removes air, allowing atmospheric pressure to push liquid up.
✅ Statement 3 – Correct: Blotting paper absorbs ink/liquid through capillary action in its porous structure and fine fibres.
✅ Statement 4 – Correct: Tall trees depend on capillary action to transport water from roots to leaves against gravity through xylem vessels.
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