SSC CGL Science – Units, Measurement & Physical Quantities – Level 3 · Challenge
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Symbols W, J, N are capitals (Watt, Joule, Newton); mol is small – the mole is not named after a person.
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SSC CGL Science – Units, Measurement & Physical Quantities – Level 3 · Challenge – 8 questions, subject: General Science. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.
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1.
Reverse questionWhich equation is dimensionally WRONG? (v, u velocities; a acceleration; s distance; t time)
Correct Answer: D [v = u + at²]
Explanation:
at² has dimensions [LT⁻²][T²] = [L], not [LT⁻¹], so it cannot be added to a velocity.
2.
The speed of a deep-water wave depends on g and the wavelength λ as v ∝ gᵃ λᵇ. By dimensional analysis a and b are:
Correct Answer: A [a = ½, b = ½]
Explanation:
[LT⁻¹] = [LT⁻²]ᵃ[L]ᵇ → T: −2a = −1, L: a + b = 1 → a = ½, b = ½ (v ∝ √(gλ)).
3.
The mass and speed of a ball are measured with errors of 1% and 4%. The maximum error in its kinetic energy is:
Correct Answer: C [9%]
Explanation:
KE = ½mv² → 1% + 2 × 4% = 9% (½ has no error).
4.
Using dimensions, 1 joule converted into the CGS unit (erg) is:
Correct Answer: D [10⁷ erg]
Explanation:
[ML²T⁻²]: 1 kg = 10³ g, 1 m = 10² cm → 10³ × (10²)² = 10⁷ erg.
5.
Spot My Mistake“0.0500 m has only one significant figure, because the zeros are not significant.” How many significant figures does 0.0500 really have?
Correct Answer: B [3]
Explanation:
Leading zeros do not count, but the two trailing zeros after the decimal point do → 5, 0, 0 = 3.
6.
Reverse questionJ s (joule-second) is the SI unit of which of these?
Correct Answer: A [Planck constant]
Explanation:
Answer: Planck constant. E = hν → h = E/ν, unit J s.
7.
A student takes three readings 7.81 cm, 7.80 cm and 7.82 cm of a length whose true value is 7.20 cm. The readings are:
Correct Answer: D [precise but not accurate]
Explanation:
They agree closely with each other (precise) but are far from 7.20 cm (not accurate) – a sign of systematic error.
8.
Which of the following units is NOT named after a scientist?
Correct Answer: B [mole]
Explanation:
Symbols W, J, N are capitals (Watt, Joule, Newton); mol is small – the mole is not named after a person.
➤ Full notes, shortcuts and every answer explained – SSC CGL 2026 General Science book (₹149): www.shanmugamiasacademy.in/study-materials/ssc-cgl-general-science
📘 SSC CGL 2026 – General Science (Tier I + Tier II)
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