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Motion of a system of particles and rigid bodies is a fundamental topic in physics that deals with the movement of multiple objects or particles. Here’s a brief overview:

1. **System of Particles:** A system of particles refers to a collection of particles whose motion is considered together as a single entity. The motion of each particle is affected by external forces as well as internal forces between particles in the system.

2. **Centre of Mass:** The centre of mass of a system of particles is the point that moves as though all the mass of the system were concentrated at that point and all external forces were applied there. The motion of the centre of mass is affected by external forces only.

3. **Linear Momentum:** The linear momentum of a system of particles is the product of the total mass of the system and the velocity of its centre of mass. It is conserved if the net external force acting on the system is zero.

4. **Angular Momentum:** The angular momentum of a system of particles about a fixed axis is the sum of the angular momenta of the individual particles. It is conserved if the net external torque acting on the system is zero.

5. **Rigid Body:** A rigid body is an object whose shape and size do not change under the action of external forces. The motion of a rigid body can be described by its translational motion (motion of its centre of mass) and its rotational motion (rotation about its centre of mass).

6. **Rotational Motion:** The rotational motion of a rigid body is described in terms of its angular displacement, angular velocity, and angular acceleration. The relationship between these quantities is given by the equations of rotational motion.

7. **Moments of Inertia:** The moment of inertia of a rigid body is a measure of its resistance to rotational motion. It depends on the distribution of mass in the body and the axis of rotation.

8. **Torque:** Torque is the rotational analogue of force. It is the product of the force and the perpendicular distance from the axis of rotation to the line of action of the force. It causes a change in the angular momentum of a body.

Understanding the motion of systems of particles and rigid bodies is important in various fields, including physics, engineering, and biomechanics, as it allows us to analyze and predict the motion of complex systems.