Acting in the opposite direction to particle motion is friction.
V depends on the particular machine and on the speed of rotation.
10 -13 sec. Its S value was known before its function or molecular weight, and so has become its name. The molecules of larger S value go farther because of eithe r larger molecular weight or less frictional drag or both. You stop the centrifuge when the different molecules have traveled different distances down the tube and then remove the solution by puncturing the bottom of the tube or pumping the solution off t he top. Today there are many other methods also used, as listed below.