Make Fluxion with the speed squared of body i

def flux_v2(v_vars: List[fl.Var], i: int):
    """Make Fluxion with the speed squared of body i"""
    # Index with the base of (v_x, v_y, v_z) for body i
    k = 3*i
    # The speed squared of body i
    return fl.square(v_vars[k+0]) + fl.square(v_vars[k+1]) + fl.square(v_vars[k+2])