Skip to content
Parchaاردو

Sample questions · Every question here is a sample written by Parcha and not yet checked by a subject reviewer. Check important answers against your textbook. How we write questions

Physical science basics MCQs

PPSC / FPSC / NTS · Everyday science · 6 questions

Practise 6 questionsNot started

Untimed, with instant feedback. Answers are saved on this phone.

Revision summary

A handful of physical-science facts appear in almost every general test. Light travels at about 3 × 10⁸ m/s in a vacuum, while sound travels at about 340 m/s in air and cannot cross a vacuum. Pure water has pH 7 at 25 °C; below 7 is acidic (lemon juice, stomach acid) and above 7 basic (soap, baking soda). Water boils at 100 °C at sea level and at lower temperatures higher up, because air pressure falls with altitude; it freezes at 0 °C. Air is about 78% nitrogen, 21% oxygen, 0.9% argon and 0.04% carbon dioxide. The ozone layer, in the stratosphere about 15 to 35 km up, absorbs most ultraviolet radiation. SI units are favourite distractors: current in amperes, potential difference in volts, resistance in ohms, power in watts, energy in joules, force in newtons and pressure in pascals. When two options look right, check whether the question asks for a unit or a quantity.

Questions with answers

Written by Parcha from the syllabus. Samples until a subject reviewer checks them; report anything wrong from the practice screen.

  1. Q1 · Parcha original · Sample

    The speed of light in a vacuum is about:

    • A. 3 × 10⁸ m/s
    • B. 3 × 10⁶ m/s
    • C. 340 m/s
    • D. 3 × 10⁵ m/s
    Show answer

    Answer: A. 3 × 10⁸ m/s

    Light travels at about 3 × 10⁸ m/s (300,000 km/s) in a vacuum. 340 m/s is roughly the speed of sound in air.

    Open this question on its own page

  2. Q2 · Parcha original · Sample

    The pH of pure water at 25 °C is:

    • A. 0
    • B. 5
    • C. 7
    • D. 14
    Show answer

    Answer: C. 7

    Pure water is neutral, with pH 7 at 25 °C. Below 7 is acidic and above 7 is basic (alkaline).

  3. Q3 · Parcha original · Sample

    Most of the ozone layer lies in the:

    • A. Troposphere
    • B. Mesosphere
    • C. Thermosphere
    • D. Stratosphere
    Show answer

    Answer: D. Stratosphere

    The ozone layer is in the stratosphere, roughly 15 to 35 km above the ground. It absorbs most of the Sun's harmful ultraviolet radiation.

  4. Q4 · Parcha original · Sample

    The most abundant gas in Earth's atmosphere is:

    • A. Oxygen
    • B. Nitrogen
    • C. Carbon dioxide
    • D. Argon
    Show answer

    Answer: B. Nitrogen

    Dry air is about 78% nitrogen, 21% oxygen and 0.9% argon; carbon dioxide is only about 0.04%.

  5. Q5 · Parcha original · Sample

    The SI unit of electric current is the:

    • A. Volt
    • B. Ohm
    • C. Ampere
    • D. Watt
    Show answer

    Answer: C. Ampere

    Current is measured in amperes (A), one of the seven SI base units. The volt measures potential difference, the ohm resistance, and the watt power.

  6. Q6 · Parcha original · Sample

    At sea level, pure water boils at:

    • A. 90 °C
    • B. 100 °C
    • C. 110 °C
    • D. 120 °C
    Show answer

    Answer: B. 100 °C

    At standard sea-level pressure, pure water boils at 100 °C. At higher altitudes the air pressure is lower, so water boils at a lower temperature (that is why cooking is slower in the mountains).