SSC CGL Science – Units, Measurement & Physical Quantities – Tier II Level · Marathon

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SSC CGL Science – Units, Measurement & Physical Quantities – Tier II Level · Marathon – 11 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.  
A vernier callipers has a positive zero error of 0.04 cm. The observed reading for a rod is 2.53 cm. The correct length is:

Correct Answer: C [2.49 cm]

Explanation:

Correct = observed − zero error = 2.53 − 0.04 = 2.49 cm.

2.  
A screw gauge has pitch 0.5 mm and 50 circular divisions. The main-scale reading is 6.5 mm and the 12th circular division is on the index line. The reading is:

Correct Answer: A [6.62 mm]

Explanation:

LC = 0.5/50 = 0.01 mm; reading = 6.5 + 12 × 0.01 = 6.62 mm.

3.  
A force is given by F = at + bt², where t is time. The dimensions of b are:

Correct Answer: D [[MLT⁻⁴]]

Explanation:

bt² must be a force: [b] = [MLT⁻²]/[T²] = [MLT⁻⁴].

4.  
In a pendulum experiment, g = 4π²l/T². If the errors in l and T are 1% and 0.5%, the maximum error in g is:

Correct Answer: A [2%]

Explanation:

1% + 2 × 0.5% = 2% (4π² is exact).

5.  
In a new system the unit of mass is 2 kg, the unit of length is 3 m and the unit of time is 6 s. Then 1 N equals how many new units of force?

Correct Answer: B [6]

Explanation:

New unit of force = 2 kg × 3 m ÷ (6 s)² = 1/6 N, so 1 N = 6 new units.

6.  
Applying the rules of significant figures, 3.5 + 12.06 + 0.427 = ?

Correct Answer: C [16.0]

Explanation:

In addition keep the least number of decimal places (3.5 has one) → 15.987 → 16.0 (the trailing 0 shows the tenths place).

7.  
Rounded off to three significant figures (NCERT rule for a dropped 5), 2.745 becomes:

Correct Answer: D [2.74]

Explanation:

The digit dropped is 5 and the preceding digit (4) is even, so it is left unchanged → 2.74.

8.  
Assertion–ReasonAssertion (A): Every dimensionally correct equation is physically correct.
Reason (R): Dimensional analysis cannot find pure-number constants.

Correct Answer: B [A is false but R is true]

Explanation:

s = ut + at² is dimensionally correct but wrong (½ missing) – exactly because dimensions cannot test numbers.

9.  
Which of these distances is the largest?

Correct Answer: A [1 parsec]

Explanation:

AU ≈ 1.5 × 10¹¹ m < 10¹² m < ly ≈ 9.46 × 10¹⁵ m < parsec ≈ 3.09 × 10¹⁶ m.

10.  
The length and breadth of a rectangle are (5.0 ± 0.1) cm and (2.0 ± 0.1) cm. The maximum percentage error in its area is:

Correct Answer: C [7%]

Explanation:

0.1/5.0 = 2% and 0.1/2.0 = 5%; for a product the % errors add → 7%.

11.  
Data tableA student records the diameter of a wire with a screw gauge (LC 0.01 mm) five times: 2.20, 2.21, 2.19, 2.20, 2.20 mm. The best estimate of the diameter is:

Correct Answer: C [2.20 mm]

Explanation:

Mean = 11.00 ÷ 5 = 2.20 mm; keep two decimal places to match the least count.

➤ Full notes, shortcuts and every answer explained – SSC CGL 2026 General Science book (₹149): www.shanmugamiasacademy.in/study-materials/ssc-cgl-general-science

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