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System of Particles and Rotational Motion

JEE Main 2026 (Online) 24th January Evening ShiftMCQMedium📈 Topic in 22% papers+4−1
Ques. 1JEE Main 2026, 24 January (Evening Shift)

A thin uniform rod (X) of mass M and length L is pivoted at a height ( L3 ) as shown in the figure. The rod is allowed to fall from a vertical position and lie horizontally on the table. The angular velocity of this rod when it hits the table top, is . (g = gravitational acceleration) [figure]

  1. 32 gL
  2. 3gL
  3. 3 2 gL
  4. 1 2 gL

Answer

(2) 3gL

Solution

The rod rotates about the pivot, which is L3 from its lower end, while its centre of mass is L2 from the lower end, so the distance from the pivot is d = L2 - L3 = L6.

Initially the centre of mass is L6 above the pivot and on the table it is at the level of the pivot, so it falls through h = L6.

By the parallel axis theorem, the moment of inertia about the pivot is

I = ML212 + M ( L6 )2 = 3ML2 + ML236 = ML29

Energy conservation, 12I 2 = Mgh, gives

12 ML29 2 = Mg L6

2 = 3gL

= 3gL

Answer: (2)

Keep practising — System of Particles and Rotational Motion

Ques. 2JEE Main 2026, 24 January (Evening Shift)

A uniform solid cylinder of length L and radius R has moment of inertia about its axis equal to I1. A small concentric cylinder of length L/2 and radius R/3 carved from this cylinder has moment of inertia about its axis equal to I2. The ratio I1/I2 is .

Ques. 3JEE Main 2026, 23 January (Morning Shift)

Two small balls with masses m and 2m are attached to both ends of a rigid rod of length d and negligible mass. If angular momentum of this system is L about an axis (A) passing through its centre of mass and perpendicular to the rod then angular velocity of the system about A is :

  1. 43 Lmd2
  2. 32 Lmd2
  3. 2L5md2
  4. 2Lmd2
Ques. 4JEE Main 2026, 23 January (Morning Shift)

The moment of inertia of a square loop made of four uniform solid cylinders, each having radius R and length L (R < L) about an axis passing through the mid points of opposite sides, is (Take the mass of the entire loop as M):

  1. 34MR2 + 16ML2
  2. 38MR2 + 712ML2
  3. 34MR2 + 712ML2
  4. 38MR2 + 16ML2
Ques. 5JEE Main 2026, 23 January (Evening Shift)

Suppose there is a uniform circular disc of mass M kg and radius r m shown in figure. The shaded regions are cut out from the disc. The moment of inertia of the remainder about the axis A of the disc is given by x256 M r2. The value of x is . [figure]

Ques. 6JEE Main 2026, 22 January (Morning Shift)

A solid sphere of mass 5 kg and radius 10 cm is kept in contact with another solid sphere of mass 10 kg and radius 20 cm. The moment of inertia of this pair of spheres about the tangent passing through the point of contact is kg m2.

  1. 0.18
  2. 0.72
  3. 0.36
  4. 0.63
Ques. 7JEE Main 2026, 22 January (Morning Shift)

A circular disc has radius R1 and thickness T1. Another circular disc made of the same material has radius R2 and thickness T2. If the moments of inertia of both discs are the same and R1R2 = 2 then T1T2 = 1 . The value of is .

Ques. 8JEE Main 2026, 22 January (Evening Shift)

A uniform bar of length 12 cm and mass 20 m lies on a smooth horizontal table. Two point masses m and 2m are moving in opposite directions with same speed of v and in the same plane as the bar, as shown in figure. These masses strike the bar simultaneously and get stuck to it. After collision the entire system is rotating with angular frequency . The ratio of v and is : [figure]

  1. 33
  2. 2 88
  3. 32
  4. 66
Ques. 9JEE Main 2026, 22 January (Evening 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 false but Statement II is true
  3. Statement I is true but Statement II is false
  4. Both Statement I and Statement II are true
Ques. 10JEE Main 2026, 22 January (Evening Shift)

Two masses m and 2m are connected by a light string going over a pulley (disc) of mass 30m with radius r = 0.1 m. The pulley is mounted in a vertical plane and it is free to rotate about its axis. The 2m mass is released from rest and its speed when it has descended through a height of 3.6 m is m/s. (Assume string does not slip and g = 10 m/s2)

Ques. 11JEE Main 2026, 21 January (Morning Shift)

A uniform rod of mass m and length l is suspended by means of two identical inextensible light strings as shown in figure. Tension in one string immediately after the other string is cut, is . (g acceleration due to gravity) [figure]

  1. mg/3
  2. mg/4
  3. mg
  4. mg/2

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