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NCERT Solutions for Class 11 Physics Ch-6: System of Particles and Rotational Motion
NCERT Solutions for Class 11 Physics Chapter 6 System of Particles and Rotational Motion introduces the concept of centre of mass, torque, angular momentum, moment of inertia, and the equilibrium and rolling motion of rigid bodies.
Overview of Topics & Subtopics
Important Questions and Answers
Q1: What is meant by the centre of mass of a system of particles?
Answer: The centre of mass of a system of particles is a hypothetical point where the entire mass of the system can be considered to be concentrated for the purpose of analyzing its translational motion; it moves as though all external forces on the system are acting at this single point.
Q2: Define torque and state the condition for rotational equilibrium.
Answer: Torque is the moment of a force about a given axis, defined as τ = r × F, representing the turning effect of a force. A rigid body is in rotational equilibrium when the net external torque acting on it about any axis is zero, resulting in no angular acceleration.
Q3: State the theorem of parallel axes for moment of inertia.
Answer: The theorem of parallel axes states that the moment of inertia of a body about any axis is equal to its moment of inertia about a parallel axis passing through its centre of mass, plus the product of its mass and the square of the perpendicular distance between the two axes: I = Icm + Md².
Q4: State the law of conservation of angular momentum.
Answer: The law of conservation of angular momentum states that if no external torque acts on a system, its total angular momentum remains constant. This principle explains phenomena such as an ice-skater spinning faster when they pull their arms inward.
Q5: What condition must be satisfied for a rigid body to be in rolling motion without slipping?
Answer: For rolling without slipping, the velocity of the point of contact of the rolling body with the surface must be zero at every instant, which is satisfied when the linear velocity of the centre of mass equals the product of the angular velocity and the radius, v = ωR.
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