Chapter Exam

Chapter-6 System of Particles and Rotational Motion — Online MCQ Test

Q: The centre of mass of a system of particles is defined as the point where the entire mass of the system can be considered to be concentrated. Which of the following correctly represents the position of centre of mass?

Answer: A. r_cm = (Σm_i r_i)/(Σm_i) — The position of centre of mass is the weighted average of positions of all particles, given by r_cm = (Σm_i r_i)/(Σm_i), where m_i is the mass of each particle and r_i is its position vector.

Q: A rigid body has both translational and rotational motion. Its total kinetic energy is:

Answer: C. KE_total = (1/2)Mv_cm² + (1/2)Iω² — Total kinetic energy of a rigid body is the sum of translational kinetic energy (1/2)Mv_cm² and rotational kinetic energy (1/2)Iω² about the centre of mass.

Q: In a collision between two particles, the centre of mass experiences:

Answer: A. No acceleration if external force is zero — The centre of mass acceleration depends only on external forces (a_cm = F_external/M_total), not on internal collision forces. If F_external = 0, then a_cm = 0.

PHYSICS · Grade 11 · CBSE(NCERT)

Practice Chapter-6 System of Particles and Rotational Motion with a free chapter-wise online MCQ test for CBSE(NCERT) Grade 11 PHYSICS. This chapter covers: Centre of mass - Momentum conservation - Centre of mass motion - Torque - Angular momentum - Conservation of angular momentum - Equilibrium of rigid bodies - Moment of inertia - Ra.... AI-generated questions from basic to board-exam level, with instant results and explanations.

Questions

20m

Time Limit

Attempts Left

10 random questions from this chapter (mixed difficulty)
Questions you've seen before won't repeat until the pool resets
You have 20 minutes — exam auto-submits when time is up
Maximum 3 attempts per chapter
Results and explanations shown immediately after submission

New here? Register free — includes 3 free chapter exams.

Chapter-6 System of Particles and Rotational Motion — Important Questions & Answers (FAQ)

Frequently asked questions from CBSE(NCERT) Grade 11 PHYSICS — Chapter-6 System of Particles and Rotational Motion, with answers and explanations. These are sample questions; the exam has its own separate question set.

The centre of mass of a system of particles is defined as the point where the entire mass of the system can be considered to be concentrated. Which of the following correctly represents the position of centre of mass?

A. r_cm = (Σm_i r_i)/(Σm_i) ✓
B. r_cm = (Σr_i)/(Σm_i)
C. r_cm = (Σm_i)/(Σm_i r_i)
D. r_cm = (Σm_i r_i²)/(Σm_i)

Answer: A. r_cm = (Σm_i r_i)/(Σm_i)
The position of centre of mass is the weighted average of positions of all particles, given by r_cm = (Σm_i r_i)/(Σm_i), where m_i is the mass of each particle and r_i is its position vector.

Which one of the following is NOT a consequence of conservation of momentum?

A. In the absence of external force, the momentum of a system remains constant
B. The centre of mass of an isolated system moves with constant velocity
C. The velocity of each particle in a system always remains constant ✓
D. Newton's third law can be derived from momentum conservation

Answer: C. The velocity of each particle in a system always remains constant
While momentum of a system is conserved in the absence of external force, individual particles can change their velocities as long as the total momentum remains constant. Option C incorrectly claims all particles maintain constant velocity.

A rigid body has both translational and rotational motion. Its total kinetic energy is:

A. KE_total = (1/2)Mv_cm²
B. KE_total = (1/2)Iω²
C. KE_total = (1/2)Mv_cm² + (1/2)Iω² ✓
D. KE_total = Mv_cm² + Iω²

Answer: C. KE_total = (1/2)Mv_cm² + (1/2)Iω²
Total kinetic energy of a rigid body is the sum of translational kinetic energy (1/2)Mv_cm² and rotational kinetic energy (1/2)Iω² about the centre of mass.

For a rigid body in pure rolling motion on a horizontal surface, which statement is correct?

A. The instantaneous axis of rotation is at the geometrical centre
B. The instantaneous axis of rotation is at the point of contact with the surface ✓
C. There is no instantaneous axis of rotation
D. The instantaneous axis of rotation changes with time

Answer: B. The instantaneous axis of rotation is at the point of contact with the surface
In pure rolling, the point of contact with the ground has zero instantaneous velocity, making it the instantaneous axis of rotation about which the body appears to be purely rotating.

In a collision between two particles, the centre of mass experiences:

A. No acceleration if external force is zero ✓
B. Infinite acceleration due to collision forces
C. An acceleration due to internal collision forces
D. A deceleration proportional to the impact

Answer: A. No acceleration if external force is zero
The centre of mass acceleration depends only on external forces (a_cm = F_external/M_total), not on internal collision forces. If F_external = 0, then a_cm = 0.