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Units and Measurements

JEE Main 2026 (Online) 23rd January Evening ShiftNumericalMedium📈 Topic in 21% papers+4
Ques. 1JEE Main 2026, 23 January (Evening Shift)

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 .

Answer

1

Solution

Dimensions: [ ] = [ ] = ML-3, [r] = L, [ ] = ML-1T-1

T = ( ML-3)a+d Lb ( ML-1T-1)c

T: -c = 1 c = -1

M: a + d + c = 0 a + d = 1

L: -3(a + d) + b - c = 0 b = 3 - 1 = 2

b + ca + d = 2 - 11 = 1

(Check: time constant = m6 r = 2 r29 , i.e. a = 1, b = 2, c = -1, d = 0.)

Answer: 1

Keep practising — Units and Measurements

Ques. 2JEE Main 2026, 22 January (Morning Shift)

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
Ques. 3JEE Main 2026, 21 January (Morning Shift)

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%
Ques. 4JEE Main 2026, 21 January (Morning Shift)

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]
Ques. 5JEE Main 2026, 21 January (Evening Shift)

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
Ques. 6JEE Main 2026, 21 January (Evening Shift)

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
Ques. 7JEE Main 2025, 8 April (Evening Shift)

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
Ques. 8JEE Main 2025, 7 April (Evening Shift)

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
Ques. 9JEE Main 2025, 7 April (Evening Shift)

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

  1. (A)-(IV), (B)-(II), (C)-(III), (D)-(I)
  2. (A)-(II), (B)-(III), (C)-(IV), (D)-(I)
  3. (A)-(IV), (B)-(III), (C)-(I), (D)-(II)
  4. (A)-(IV), (B)-(II), (C)-(I), (D)-(III)
Ques. 10JEE Main 2025, 4 April (Morning Shift)

In an electromagnetic system, the quantity representing the ratio of electric flux and magnetic flux has dimension of MP LQ TR AS, where value of 'Q' and 'R' are

  1. (3, -5)
  2. (-2, 1)
  3. (-2, 2)
  4. (1, -1)
Ques. 11JEE Main 2025, 4 April (Evening Shift)

In an electromagnetic system, a quantity defined as the ratio of electric dipole moment and magnetic dipole moment has dimension of [MP LQ TR AS ]. The values of P and Q are :

  1. -1, 0
  2. 0, -1
  3. -1, 1
  4. 1, -1

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