A particle is moving freely. Then its

A free particle is defined as one that is not subject to any external forces or fields. In classical physics, this implies the particle exists in a 'field-free' space where its potential energy is uniform and can be arbitrarily set to zero. Kinetic energy is defined as the energy of motion, calculated as (1/2)mv². Since mass (m) is always positive and the square of velocity (v²) is non-negative, kinetic energy must be greater than or equal to zero [1]. For a particle in motion, the kinetic energy is strictly greater than zero. Conversely, potential energy is energy stored by virtue of position or configuration in a field [1]. Because a free particle experiences no forces, it has no potential energy (V=0), and its total energy consists entirely of its kinetic energy. Therefore, kinetic energy is always greater than zero for a moving free particle.

Sources

1. [1] https://web.chem.ox.ac.uk/teaching/Physics%20for%20CHemists/Mechanics/energy.html