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JEE Advanced Physics Rotational Motion 2022 JEE Advanced 2022 (Paper 1)

JEE Advanced Physics Question (2022) — Solution

Question

A solid sphere of mass 1   kg and radius 1   m rolls without slipping on a fixed inclined plane with an angle of inclination θ = 30 ° from the horizontal. Two forces of magnitude 1   N  each, parallel to the incline, act on the sphere, both at distance r = 0 . 5   m from the center of the sphere, as shown in the figure. The acceleration of the sphere down the plane is m   s - 2 . (Take g = 10   m   s - 2 ) If the numerical value has more than two decimal places, truncate/round-off the value to TWO decimal places.

Options

  1. A. A
  2. B. B
  3. C. C
  4. D. D

Answer

A. A

Step-by-step solution

The forces acting on the solid sphere is shown below. Here,  N  is the normal force acting on sphere and weight  m g  is acting downwards.    Taking torque about contact point. τ → = m g R sin 30 ⊗ + 1 × 1 ⊙ = 10 × 1 × 1 2 - 1       (Taking ⊗  as positive) Then, we have  ⇒ 5 - 1 = I sphere about tangent α Using parallel axis theorem, τ = 2 5 m R 2 + m R 2 α = 7 5 m R 2 α ⇒ α = 20 7 rad   s - 2 So, acceleration of sphere down the plane is  a cm = α R = 20 7   m   s - 2 a cm = 2 . 86   m   s - 2

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