Velocity and viscosity.

viscosity, terminal velocity

1. To demonstrate that two liquids can have a large difference in viscosity by showing the rates for metal spheres falling through different liquids. 2. To show how terminal velocity is affected by change in radius and change in density.

special lucite apparatus, small steel ball bearings, steel and glass spheres of nearly the same radius

Two vertical tubes are built into a lucite container together with a vertical scale. The two tubes can be filled with two oils (or liquids) of differing viscosity and identical spheres released at the top surface at the same time are seen to have differing terminal velocities. Using one of the oils, two spheres of differing radii can be dropped to demonstrate that the larger radius sphere has the larger terminal velocity (The terminal velocities if measured are not found to be proportional to the square of the radius as the spheres are not falling in an infinite medium). For spheres of equal radii but different density, an experiment with a glass bead and a steel sphere of the same radius will show that the steel sphere of greater density has the higher terminal velocity.