Each  ribosome  having  of two  subunits  a small  subunit  and  a large  subunit, every of that is a multi component  complex  of rRNAs (ribosomal  RNAs)  and ribosomal proteins that is given in the figure. One way of distinguishing  between particles like as ribosomes  and  ribosomal  subunits  is  to  place  the  sample  in  a  tube  within  a centrifuge  rotor  and spin  this at very  high  speed.  That causes the particles to sediment to the tube bottom. Particles which vary in mass shape and density sediment at variant velocities (sedimentation velocities).  Thus a particle with double the mass of another will always sediment faster give both particles have the same density and shape.