SSC CGL Science – Units, Measurement & Physical Quantities – Level 2 · Exam Level · Tier I Sprint

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SSC CGL Science – Units, Measurement & Physical Quantities – Level 2 · Exam Level · Tier I Sprint – 15 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.  
In a vernier callipers, 20 vernier divisions equal 19 main-scale divisions of 1 mm each. Its least count is:

Correct Answer: C [0.05 mm]

Explanation:

LC = 1 MSD − 1 VSD = 1 − 19/20 = 1/20 = 0.05 mm.

2.  
Diagram-basedThe figure shows a vernier callipers (least count 0.01 cm). What is the reading?

Correct Answer: D [3.26 cm]

Explanation:

Main scale 3.2 cm; 6th vernier mark coincides → 3.2 + 6 × 0.01 = 3.26 cm.

3.  
A screw gauge has pitch 1 mm and 100 circular divisions. The sleeve reads 4 mm and the 72nd division is on the index line. The reading is:

Correct Answer: A [4.72 mm]

Explanation:

LC = 1/100 = 0.01 mm; reading = 4 + 72 × 0.01 = 4.72 mm.

4.  
Match the followingMatch the instruments with what they measure:
P. Anemometer Q. Barometer R. Seismograph S. Lactometer
1. Atmospheric pressure 2. Purity of milk 3. Speed of wind 4. Earthquake waves

Correct Answer: B [P-3, Q-1, R-4, S-2]

Explanation:

Anemometer – wind speed; barometer – atmospheric pressure; seismograph – earthquake waves; lactometer – milk purity.

5.  
The dimensional formula of pressure is:

Correct Answer: A [[ML⁻¹T⁻²]]

Explanation:

Pressure = force ÷ area = [MLT⁻²]/[L²] = [ML⁻¹T⁻²].

6.  
Which pair of quantities has the same dimensions?

Correct Answer: B [Work and torque]

Explanation:

Work and torque are both force × distance → [ML²T⁻²].

7.  
1 pascal (1 N/m²) expressed in CGS units is:

Correct Answer: D [10 dyne/cm²]

Explanation:

1 N = 10⁵ dyne and 1 m² = 10⁴ cm² → 10⁵ ÷ 10⁴ = 10 dyne/cm².

8.  
Assertion–ReasonAssertion (A): The light year is a unit of distance.
Reason (R): It is the distance travelled by light in vacuum in one year.

Correct Answer: C [Both A and R are true and R explains A]

Explanation:

R is the definition that makes the light year a distance.

9.  
The radius of a sphere is measured with a 2% error. The maximum error in its volume is:

Correct Answer: B [6%]

Explanation:

Answer: 6%. V = (4/3)πr³ → 3 × 2% = 6%.

10.  
Odd one out

Correct Answer: C [kelvin]

Explanation:

Angstrom, fermi and parsec are units of length; kelvin is the unit of temperature.

11.  
Arrange in orderArrange in increasing order of size: micron, angstrom, fermi, nanometre

Correct Answer: A [fermi < angstrom < nanometre < micron]

Explanation:

fermi 10⁻¹⁵ m < angstrom 10⁻¹⁰ m < nanometre 10⁻⁹ m < micron 10⁻⁶ m.

12.  
Two-quantity comparison
Quantity I: 1 parsec
Quantity II: 3 light years

Correct Answer: A [Quantity I > Quantity II]

Explanation:

1 parsec ≈ 3.26 light years, which is more than 3 light years.

13.  
Using the rule of significant figures, 3.62 × 1.4 should be written as:

Correct Answer: D [5.1]

Explanation:

Product keeps the least number of significant figures (1.4 has 2) → 5.068 → 5.1.

14.  
Which of the following is dimensionless?

Correct Answer: C [Strain]

Explanation:

Strain = change in length ÷ original length – a pure ratio.

15.  
True/false countHow many of these statements about the 2019 SI are true?
I. The Planck constant fixes the kilogram.
II. The speed of light fixes the metre.
III. The Avogadro constant fixes the mole.
IV. The Boltzmann constant fixes the candela.

Correct Answer: B [3]

Explanation:

I, II, III are true. The Boltzmann constant fixes the kelvin; the candela is fixed by the luminous efficacy 683 lm/W.

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