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Units and Measurements · Question 21

JEE Main 2026 (Online) 24th January Evening ShiftMCQEasy📈 Topic in 26% papers+4−1
1

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

Answer

(1) 0.002

Solution

50 VSD = 48 MSD 1 VSD = 4850 MSD

Least count = 1 MSD - 1 VSD = (1 - 4850 )MSD

LC = 250 0.05 mm

LC = 0.002 mm

Answer: (1)

JEE Main 2026 (Online) 24th January Evening Shift

Keep practising — Units and Measurements

2

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
3

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
4

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
5

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
6

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
7

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
8

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
9

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
10

A quantity Q is formulated as X-2Y+ 32Z- 25. X, Y, and Z are independent parameters which have fractional errors of 0.1, 0.2, and 0.5, respectively in measurement. The maximum fractional error of Q is

  1. 0.6
  2. 0.8
  3. 0.7
  4. 0.1
JEE Main 2025 (Online) 8th April Evening Shift
11

The dimension of 0 0 is equal to that of: ( 0 = Vacuum permeability and 0 = Vacuum permittivity)

  1. Voltage
  2. Inductance
  3. Resistance
  4. Capacitance
JEE Main 2025 (Online) 7th April Evening Shift

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