def specific_kinetic_energy(particles):
    """
    Returns the specific kinetic energy of each particle in the set.

    >>> from amuse.datamodel import Particles
    >>> particles = Particles(2)
    >>> particles.vx = [1.0, 1.0] | units.ms
    >>> particles.vy = [0.0, 0.0] | units.ms
    >>> particles.vz = [0.0, 0.0] | units.ms
    >>> particles.mass = [1.0, 1.0] | units.kg
    >>> particles.specific_kinetic_energy()
    quantity<[0.5, 0.5] m**2 * s**-2>
    """

    return 0.5*(particles.vx**2+particles.vy**2+particles.vz**2)