Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main202622 January 2026Morning ShiftPhysicsRotational MotionActual

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 . m ² .

Options

  1. A0.72
  2. B0.36
  3. C0.18
  4. D0.63

Correct answer

D. 0.63

Step-by-step solution

For two solid spheres in contact with the tangent line at the contact point. Sphere 1: m₁ = 5 kg, r₁ = 0.1 m Sphere 2: m₂ = 10 kg, r₂ = 0.2 m For a solid sphere, I_ cm = 2 5 mr^2 The tangent at contact is perpendicular to the line joining centers. The perpendicular distance from each sphere's center to this tangent line equals its radius. Using parallel axis theorem: I_ total = I_ cm + md^2 For sphere 1: I₁ = 2 5 (5)(0.1)^2 + 5(0.1)^2 = 0.02 + 0.05 = 0.07 kg·m² For sphere 2: I₂ = 2 5 (10)(0.2)^2 + 10(0.2)^2 = 0.16

Practice Rotational Motion on Quantrex Academy →

More from Rotational Motion

Consider a large disk of radius R and two smaller disks, each of radius r = R/50 , lying on its circumference, as shown in the figure. The smaller disks are initially in contact wi 2026A solid cylinder of radius R rolls without slipping with a center of mass speed v₀ = gR 3 on a horizontal surface with a vertical edge, as shown in the figure. Here, g is the accel 2026List-I shows four planar structures made of uniform solid rods each of mass m and length l . In the List-II the possible moment of inertia of these structures about an axis OCO' , 2026Passage: A uniform circular disk of radius 0.2 m and mass 1 kg is pivoted at its top point C such that it can rotate freely around C in the XY plane, as shown in the figure. Initia 2026Passage: A uniform circular disk of radius 0.2 m and mass 1 kg is pivoted at its top point C such that it can rotate freely around C in the XY plane, as shown in the figure. Initia 2026A solid cylinder having radius R and length L is slipping on a rough horizontal plane. At time t=0 the cylinder has a translational velocity v₀=49 m/s, perpendicular to its axis an 2026A solid sphere ( A ) of mass 5m and a spherical shell ( B ) of mass m , both having same radius, are placed on a rough surface. When a force of same magnitude is applied tangential 2026A solid sphere of radius 4 cm and mass 5 kg is rotating (rotation axis is passing through the centre of the sphere) with an angular velocity of 1200 rpm. It is brought to rest in 1 2026 Full Rotational Motion list All JEE Main PYQs