The Viscosity and Particle Drag apparatus is a simple falling-sphere viscometer. The self-standing unit holds two glass tubes filled with the test fluids, for comparisons and to minimize draining and refilling of the fluids after experimentation. The back plate has a low-voltage backlight so students can easily see the test spheres through the fluid.
Students fill the two tubes with their chosen test fluid, and then select a sphere of the correct density and size for the fluid. They drop the sphere into the test fluid at the top of he glass tube. They then use a stopwatch (included) to measure the time taken for the sphere to fall a set distance down the tube.
When the test sphere reaches the bottom of the tube it enters a valve that the students turns, dropping the sphere into a collection vial for recovery. The valve system minimizes the fluid loss from the tube and helps when draining the tube after the tests are complete.

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