8.8.2 Dynamic properties of colloids (3 )Sedimentation and sedimentation equilibrium 2r2( )g 7 2) Velocity of sedimentation Gravitational force exerting on a particle Times needed for particles to settle 1 cm 4 radius time 8=37(- po)8 10 um 5.9s When the particle sediments at velocity v μm 98s the resistance force is 100nm 16h f:= fv= 6tn 10 nm 68d When the particle sediments at a constant velocity 1 nm 19y g For particles with radius less than 100 nm sedimentation is impossible due to convection and vibration of the medium2) Velocity of sedimentation Gravitational force exerting on a particle: f g r ( )g 3 4 0 3 =   −  When the particle sediments at velocity v, the resistance force is: f fv rv F = = 6 When the particle sediments at a constant velocity F g f = f  r   g v ( ) 9 2 2 0 − = radius time 10 m 5.9 s 1 m 9.8 s 100 nm 16 h 10 nm 68 d 1 nm 19 y Times needed for particles to settle 1 cm For particles with radius less than 100 nm, sedimentation is impossible due to convection and vibration of the medium. (3) Sedimentation and sedimentation equilibrium 8.8.2 Dynamic properties of colloids