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Units and Measurements

JEE Main 2024 (Online) 6th April Evening ShiftMCQMedium📈 Topic in 34% papers+4−1
Ques. 1JEE Main 2024, 6 April (Evening Shift)

In a vernier calliper, when both jaws touch each other, zero of the vernier scale shifts towards left and its 4th division coincides exactly with a certain division on main scale. If 50 vernier scale divisions equal to 49 main scale divisions and zero error in the instrument is 0.04 mm then how many main scale divisions are there in 1 cm ?

  1. 5
  2. 40
  3. 10
  4. 20

Answer

BONUS

Solution

50 VSD = 49 MSD LC = 1 MSD - 1 VSD = 150 MSD

vernier zero lies to the left of main-scale zero, the zero error is negative

4th VSD coincides ⇒ zero error = -(50 - 4) LC = -46 LC

46 150 MSD = 0.04 mm

1 MSD = 0.04 5046 = 123 mm

MSD in 1 cm = 10 23 = 230

(4 LC = 0.04 mm, giving 20, would hold only for a positive zero error.)

230 is not among the options, no option is correct ⇒ question dropped

Answer: Bonus (full marks to all who attempted)

Note: The official NTA answer key gives option (4). Our faculty team finds that no option is fully correct, so this question should be dropped (bonus: full marks to everyone who attempted it).

Keep practising — Units and Measurements

Ques. 2JEE Main 2024, 5 April (Morning Shift)

If G be the gravitational constant and u be the energy density then which of the following quantity have the dimensions as that of the uG :

  1. Gravitational potential
  2. pressure gradient per unit mass
  3. Energy per unit mass
  4. Force per unit mass
Ques. 3JEE Main 2024, 5 April (Morning Shift)

Time periods of oscillation of the same simple pendulum measured using four different measuring clocks were recorded as 4.62 s, 4.632 s, 4.6 s and 4.64 s. The arithmetic mean of these readings in correct significant figure is :

  1. 5 s
  2. 4.6 s
  3. 4.62 s
  4. 4.623 s
Ques. 4JEE Main 2024, 5 April (Evening Shift)

What is the dimensional formula of ab-1 in the equation (P + aV2 )(V - b) = RT, where letters have their usual meaning.

  1. [M6 L7 T4]
  2. [ M-1 L5 T3]
  3. [ M0 L3 T-2]
  4. [ M L2 T-2]
Ques. 5JEE Main 2024, 5 April (Evening Shift)

A vernier callipers has 20 divisions on the vernier scale, which coincides with 19th division on the main scale. The least count of the instrument is 0.1 mm. One main scale division is equal to mm.

  1. 5
  2. 2
  3. 1
  4. 0.5
Ques. 6JEE Main 2024, 4 April (Morning Shift)

The equation of stationary wave is : y=2a ( 2 ) ( 2 x ). Which of the following is NOT correct :

  1. The dimensions of nt is [L]
  2. The dimensions of n is [ LT-1]
  3. The dimensions of x is [L]
  4. The dimensions of n/ is [T]
Ques. 7JEE Main 2024, 4 April (Evening Shift)

Applying the principle of homogeneity of dimensions, determine which one is correct, where T is time period, G is gravitational constant, M is mass, r is radius of orbit.

  1. T2 = 4 2 rGM2
  2. T2 = 4 2 r3
  3. T2 = 4 2 r3GM
  4. T2 = 4 2 r2GM
Ques. 8JEE Main 2024, 1 February (Morning Shift)

10 divisions on the main scale of a Vernier calliper coincide with 11 divisions on the Vernier scale. If each division on the main scale is of 5 units, the least count of the instrument is :

  1. 511
  2. 1011
  3. 5011
  4. 12
Ques. 9JEE Main 2024, 1 February (Morning Shift)

The dimensional formula of angular impulse is :

  1. [ ML2T-2]
  2. [ ML-2T-1]
  3. [ ML2T-1]
  4. [ MLT-1]
Ques. 10JEE Main 2024, 1 February (Morning Shift)

The radius (r), length (l) and resistance (R) of a metal wire was measured in the laboratory as r=(0.35 0.05) cm R=(100 10) ohm l=(15 0.2) cm The percentage error in resistivity of the material of the wire is :

  1. 37.3\%
  2. 25.6\%
  3. 35.6\%
  4. 39.9\%
Ques. 11JEE Main 2024, 1 February (Evening Shift)

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

  1. (A)-(II), (B)-(I), (C)-(IV), (D)-(III)
  2. (A)-(IV), (B)-(III), (C)-(I), (D)-(II)
  3. (A)-(I), (B)-(II), (C)-(III), (D)-(IV)
  4. (A)-(III), (B)-(IV), (C)-(II), (D)-(I)

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