In mechanics, a rigid body is defined as a system of particles whose relative distances remain constant. This implies that the body does not change its shape during its motion, hence the name rigid body. Since all bodies have a certain degree of elasticity, a perfect rigid body is only an idealization but a very useful one, as it allows the description of two types of motion of fundamental interest in physics, i.e. translational motion and rotational motion. A rigid body undergoes translation when all of its constituent particles are moving on parallel trajectories and it undergoes rotation when all of its particles are moving on circular trajectories about an axis of rotation. It can also undergo simultaneous translation and rotation. If the rigid body only consist of a point moving in space, it has three degrees of freedom, i.e. the number of independent...