Hawai'i Space Grant Consortium, Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, 1996 Viscosity Teacher Page Purpose <\/p>\n
To determine how fluid a liquid really is by measuring its viscosity. <\/p>\n
Viscosity is an internal property of a fluid that offers resistance to flow. For example, pushing a spoon with a small force moves it easily through a bowl of water, but the same force moves mashed potatoes very slowly. In fact, one of the major differences between styles of mashed potatoes is the viscosity of the starchy mass: some people like their potatoes running and teeming with milk and butter (they are fans of low-viscosity potatoes), while others like their potatoes drier and stickier, so they almost crack rather than flow (these people are devoted to high-viscosity potatoes). <\/p>\n
Viscosity is important in volcanology. The more fluid a magma, the more likely it is to erupt. On the other hand, when more viscous (higher viscosity) lavas do erupt, they usually do so explosively. Viscosity also affects the shapes of lava flows and the mountains they erupt from. The more viscous the magma, the fatter the lava flow. Also, the more viscous the magmas a volcano erupts, the steeper the volcano. Thus, shield volcanoes like we have in Hawai'i have gentle slopes (less than 10 degrees), while stratovolcanoes like the Cascades in the northwestern mainland are much steeper (roughly 25 degrees). As expected, hawaiian volcanoes erupt more fluid lavas (called basalt) than do the Cascade volcanoes, which erupt a lava called andesite. <\/p>\n
There are many ways to measure viscosity, including attaching a torque wrench to a paddle and twisting it in a fluid, using a spring to push a rod into a fluid, and seeing how fast a fluid pours through a hole. This exercise uses one of the oldest and easiest ways: we will simply see how fast a sphere falls through a fluid. The faster the sphere falls, the lower the viscosity. This makes sense: if the fluid has a high viscosity it strongly resists flow, so the sphere falls slowly. If the fluid has a low viscosity, it offers less resistance to flow, so the ball falls faster. <\/p>\n
The measurement involves determining the velocity of the falling sphere. This is accomplished by dropping each sphere through a measured distance of fluid and measuring how long it takes to traverse the distance. Thus, you know distance and time, so you also know velocity, which is distance\/time. <\/p>\n
The formula for determining the viscosity is impressive, decorated with Greek letters and a squared term, but simply amounts to multiplying some numbers and then dividing by some others: <\/p>\n<\/p>\n
delta p = difference in density between the sphere and the liquid <\/p>\n
g = acceleration of gravity <\/p>\n
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Read the original post:<\/p>\n
Teacher Page: Viscosity - Hawai'i NASA Space Grant Consortium<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" Hawai'i Space Grant Consortium, Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, 1996 Viscosity Teacher Page Purpose To determine how fluid a liquid really is by measuring its viscosity. Viscosity is an internal property of a fluid that offers resistance to flow. For example, pushing a spoon with a small force moves it easily through a bowl of water, but the same force moves mashed potatoes very slowly. Continue reading