Chapter-6 System of Particles and Rotational Motion — Online MCQ Test
PHYSICS · CLASS 11 INTER I YEAR · Andhra State Board
Practice Chapter-6 System of Particles and Rotational Motion with a free chapter-wise online MCQ test.
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....
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Chapter-6 System of Particles and Rotational Motion — Important Questions & Answers
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.
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.
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.
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 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.
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.