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Units and Measurements · Question 19

JEE Main 2026 (Online) 28th January Evening ShiftMCQEasy📈 Topic in 26% papers+4−1
1

In an experiment, a set of readings are obtained as follows: 1.24 mm, 1.25 mm, 1.23 mm, 1.21 mm. The expected least count of the instrument used in recording these readings is mm.

  1. 0.01
  2. 0.05
  3. 0.001
  4. 0.1

Answer

(1) 0.01

Solution

Every reading is recorded up to the second decimal place in mm (1.24, 1.25, 1.23, 1.21).

The last recorded digit changes in steps of 0.01 mm, so the smallest value the instrument can measure is 0.01 mm.

Least count = 0.01 mm

Answer: (1)

JEE Main 2026 (Online) 28th January Evening Shift

Keep practising — Units and Measurements

2

Match the LIST-I with LIST-II Choose the correct answer from the options given below:

  1. A-III, B-IV, C-II, D-I
  2. A-I, B-III, C-IV, D-II
  3. A-IV, B-III, C-I, D-II
  4. A-III, B-IV, C-I, D-II
JEE Main 2026 (Online) 24th January Morning Shift
3

In a vernier callipers, 50 vernier scale divisions are equal to 48 main scale divisions. If one main scale division = 0.05 mm, then the least count of the vernier callipers is mm.

  1. 0.002
  2. 0.02
  3. 0.05
  4. 0.005
JEE Main 2026 (Online) 24th January Evening Shift
4

In a screw gauge, the zero of the circular scale lies 3 divisions above the horizontal pitch line when their metallic studs are brought in contact. Using this instrument thickness of a sheet is measured. If pitch scale reading is 1 mm and the circular scale reading is 51 then the correct thickness of the sheet is mm. [Assume least count is 0.01 mm]

  1. 1.54
  2. 1.50
  3. 1.51
  4. 1.48
JEE Main 2026 (Online) 23rd January Morning Shift
5

Four persons measure the length of a rod as 20.00 cm, 19.75 cm, 17.01 cm and 18.25 cm. The relative error in the measurement of average length of the rod is :

  1. 0.18
  2. 0.24
  3. 0.06
  4. 0.08
JEE Main 2026 (Online) 23rd January Morning Shift
6

A ball of radius r and density dropped through a viscous liquid of density and viscosity attains its terminal velocity at time t, given by t = A a rb c d, where A is a constant and a, b, c and d are integers. The value of b + ca + d is .

JEE Main 2026 (Online) 23rd January Evening Shift
7

Match the LIST-I with LIST-II Choose the correct answer from the options given below:

  1. A-III, B-II, C-IV, D-I
  2. A-I, B-IV, C-II, D-III
  3. A-II, B-I, C-IV, D-III
  4. A-II, B-IV, C-I, D-III
JEE Main 2026 (Online) 22nd January Morning Shift
8

In an experiment the values of two spring constants were measured as k1 = (10 0.2) N/m and k2 = (20 0.3) N/m. If these springs are connected in parallel, then the percentage error in equivalent spring constant is :

  1. 1.33%
  2. 2.67%
  3. 1.67%
  4. 2.33%
JEE Main 2026 (Online) 21st January Morning Shift
9

Consider a modified Bernoulli equation. (P + ABt2 ) + g(h + Bt) + 12 V2 = constant If t has the dimension of time then the dimensions of A and B are , respectively.

  1. [ ML0T-1] and [M0LT]
  2. [ ML0T-2] and [ M0LT-1]
  3. [ ML0T-2] and [ M0LT-2]
  4. [ ML0T-1] and [ M0LT-1]
JEE Main 2026 (Online) 21st January Morning Shift
10

A spherical body of radius r and density falls freely through a viscous liquid having density and viscosity and attains a terminal velocity v0. Estimated maximum error in the quantity is : (Ignore errors associated with , and g, gravitational acceleration)

  1. 2 [ rr - v0v0 ]
  2. 2 [ rr + v0v0 ]
  3. 2 rr + v0v0
  4. 2 rr - v0v0
JEE Main 2026 (Online) 21st January Evening Shift
11

Keeping the significant figures in view, the sum of the physical quantities 52.01 m, 153.2 m and 0.123 m is :

  1. 205.3 m
  2. 205 m
  3. 205.333 m
  4. 205.33 m
JEE Main 2026 (Online) 21st January Evening Shift

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