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Units and Measurements

JEE Main 2025 (Online) 24th January Morning ShiftNumericalEasy📈 Topic in 26% papers+4
Ques. 1JEE Main 2025, 24 January (Morning Shift)

The least count of a screw gauge is 0.01 mm. If the pitch is increased by 75% and number of divisions on the circular scale is reduced by 50%, the new least count will be 10-3 mm.

Answer

35

Solution

LC= pitchdivisions; p'=1.75 p, n'=0.5 n

LC'= 1.750.5 0.01=0.035 mm

=35 10-3 mm

Answer: 35

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Ques. 2JEE Main 2025, 24 January (Evening Shift)

The energy E and momentum p of a moving body of mass m are related by some equation. Given that c represents the speed of light, identify the correct equation

  1. E2=pc2+m2c4
  2. E2=pc2+m2c2
  3. E2=p2c2+m2c4
  4. E2=p2c2+m2c2
Ques. 3JEE Main 2025, 23 January (Morning Shift)

The position of a particle moving on x-axis is given by x(t)=A t+B 2t+Ct2+D, where t is time. The dimension of ABCD is

  1. L
  2. L3 T-2
  3. L2 T-2
  4. L2
Ques. 4JEE Main 2025, 23 January (Morning Shift)

The electric flux is = + where and are linear and surface charge density, respectively. ( ) represents

  1. displacement
  2. charge
  3. electric field
  4. area
Ques. 5JEE Main 2025, 23 January (Evening Shift)

The energy of a system is given as E(t)= 3e- t, where t is the time and =0.3 s-1. The errors in the measurement of and t are 1.2\% and 1.6\%, respectively. At t=5 s, maximum percentage error in the energy is :

  1. 6\%
  2. 11.6\%
  3. 4\%
  4. 8.4\%
Ques. 6JEE Main 2025, 23 January (Evening Shift)

Match 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)-(III), (D)-(IV)
  4. (A)-(IV), (B)-(III), (C)-(I), (D)-(II)
Ques. 7JEE Main 2025, 22 January (Morning Shift)

If B is magnetic field and 0 is permeability of free space, then the dimensions of (B/ 0) is

  1. MT-2A-1
  2. L-1A
  3. ML2T-2A-1
  4. LT-2A-1
Ques. 8JEE Main 2025, 22 January (Morning Shift)

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below.

  1. Both Statement I and Statement II are false
  2. Statement I is true but Statement II is false
  3. Both Statement I and Statement II are true
  4. Statement I is false but Statement II is true
Ques. 9JEE Main 2025, 22 January (Evening Shift)

Which one of the following is the correct dimensional formula for the capacitance in F ? M, L, T and C stand for unit of mass, length, time and charge respectively.

  1. [F]= [ C M-1L-2T2 ]
  2. [F]= [ C2M-2L2T2 ]
  3. [F]= [ C2M-1L-2T2 ]
  4. [F]= [ C M-2L-2T-2 ]
Ques. 10JEE Main 2025, 22 January (Evening Shift)

The maximum percentage error in the measurement of density of a wire is [Given, mass of wire =(0.60 0.003) g radius of wire =(0.50 0.01) cm length of wire =(10.00 0.05) cm]

  1. 7
  2. 8
  3. 5
  4. 4

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