Difference between revisions of "Measure Viscosity"
m (importing article from wikihow) |
m (Text replacement - "[[Category:P" to "[[Category: P") |
||
| (3 intermediate revisions by the same user not shown) | |||
| Line 1: | Line 1: | ||
Viscosity can be defined as the measurement of a liquid's resistance to flow. Consider water and molasses. Water flows relatively freely, while molasses is less fluid. Because molasses is more resistant to flow, it has a higher viscosity than water. While there are a number of methods from which to choose in deciding how to measure viscosity, perhaps the least complicated involves dropping a ball into a clear container of the liquid for which you are trying to determine viscosity. But this only works if the ball is sufficiently small that the flow around the ball is truly viscous and far from turbulent. Bubbles rising in champagne are barely small enough. The ball must also be much smaller than the container so the ball can be dropped at least 10 ball-radii from the side walls. | Viscosity can be defined as the measurement of a liquid's resistance to flow. Consider water and molasses. Water flows relatively freely, while molasses is less fluid. Because molasses is more resistant to flow, it has a higher viscosity than water. While there are a number of methods from which to choose in deciding how to measure viscosity, perhaps the least complicated involves dropping a ball into a clear container of the liquid for which you are trying to determine viscosity. But this only works if the ball is sufficiently small that the flow around the ball is truly viscous and far from turbulent. Bubbles rising in champagne are barely small enough. The ball must also be much smaller than the container so the ball can be dropped at least 10 ball-radii from the side walls. | ||
| − | [[Category:Physics]] | + | [[Category: Physics]] |
== Steps == | == Steps == | ||
=== Understanding Viscosity === | === Understanding Viscosity === | ||
| − | #Define viscosity. Viscosity measures a liquid’s resistance to flow.<ref> http://physics.info/viscosity/</ref> A fluid with high viscosity flows very slowly, like honey. A fluid with low viscosity flows quickly, like water. The unit for viscosity is a pascal second (Pa s).<ref>http://www.engineeringtoolbox.com/dynamic-absolute-kinematic-viscosity-d_412.html</ref> | + | #Define viscosity. Viscosity measures a liquid’s resistance to flow.<ref name="rf1"> http://physics.info/viscosity/</ref> A fluid with high viscosity flows very slowly, like honey. A fluid with low viscosity flows quickly, like water. The unit for viscosity is a pascal second (Pa s).<ref name="rf2">http://www.engineeringtoolbox.com/dynamic-absolute-kinematic-viscosity-d_412.html</ref> |
| − | #Define the equation for viscosity. This experiment will take measurements of a sphere and its passage through liquid to calculate viscosity. The equation for viscosity is '' [2(p<sub>s</sub>-p<sub>l</sub>)ga<sup>2</sup>]/9v'' where ''p<sub>s</sub>'' is the density of the sphere, p<sub>l</sub> is the density of the liquid, ''g'' is acceleration due to gravity, ''a'' is the radius of the sphere, and ''v'' is the velocity of the sphere.<ref>http://www.spacegrant.hawaii.edu/class_acts/Viscosity.html</ref> | + | #Define the equation for viscosity. This experiment will take measurements of a sphere and its passage through liquid to calculate viscosity. The equation for viscosity is '' [2(p<sub>s</sub>-p<sub>l</sub>)ga<sup>2</sup>]/9v'' where ''p<sub>s</sub>'' is the density of the sphere, p<sub>l</sub> is the density of the liquid, ''g'' is acceleration due to gravity, ''a'' is the radius of the sphere, and ''v'' is the velocity of the sphere.<ref name="rf3">http://www.spacegrant.hawaii.edu/class_acts/Viscosity.html</ref> |
| − | #Understand the variables in the viscosity equation. Density is mass per unit volume of an object and is designated with a ''p''. In this equation you need to measure the density of both the sphere, ''p<sub>s</sub>'', and the liquid, ''p<sub>l</sub>'', it is passing through. The radius of the sphere, ''a'', can be found by measuring the circumference of the sphere and dividing that by 2π. The acceleration due to gravity, ''g'', is a constant dependent on the atmosphere of the planet you’re on. In this case, you are on earth so ''g'' is 9.8m/s<sup>2</sup>.<ref>http://www.physicsclassroom.com/class/1DKin/Lesson-5/Acceleration-of-Gravity</ref> The velocity of the sphere, ''v'', is calculated during the experiment and is the time it takes an object to travel a specific distance in meters per second (m/s). | + | #Understand the variables in the viscosity equation. Density is mass per unit volume of an object and is designated with a ''p''. In this equation you need to measure the density of both the sphere, ''p<sub>s</sub>'', and the liquid, ''p<sub>l</sub>'', it is passing through. The radius of the sphere, ''a'', can be found by measuring the circumference of the sphere and dividing that by 2π. The acceleration due to gravity, ''g'', is a constant dependent on the atmosphere of the planet you’re on. In this case, you are on earth so ''g'' is 9.8m/s<sup>2</sup>.<ref name="rf4">http://www.physicsclassroom.com/class/1DKin/Lesson-5/Acceleration-of-Gravity</ref> The velocity of the sphere, ''v'', is calculated during the experiment and is the time it takes an object to travel a specific distance in meters per second (m/s). |
=== Measuring Viscosity === | === Measuring Viscosity === | ||
| − | #Gather the necessary materials for the experiment. To calculate viscosity of a liquid, you will need a sphere, a graduated cylinder, a ruler, a stopwatch, the liquid in question, a scale, and a calculator.<ref>https://www.teachengineering.org/view_activity.php?url=collection/cub_/activities/cub_surg/cub_surg_lesson03_activity1.xml</ref> This experiment has many steps, but when followed correctly, they will allow you to calculate the viscosity of any liquid. | + | #Gather the necessary materials for the experiment. To calculate viscosity of a liquid, you will need a sphere, a graduated cylinder, a ruler, a stopwatch, the liquid in question, a scale, and a calculator.<ref name="rf5">https://www.teachengineering.org/view_activity.php?url=collection/cub_/activities/cub_surg/cub_surg_lesson03_activity1.xml</ref> This experiment has many steps, but when followed correctly, they will allow you to calculate the viscosity of any liquid. |
#* The sphere can be a small marble or steel ball. Make sure its diameter is no greater than half the diameter of the graduate cylinder so it can easily be dropped into the cylinder. | #* The sphere can be a small marble or steel ball. Make sure its diameter is no greater than half the diameter of the graduate cylinder so it can easily be dropped into the cylinder. | ||
#* A graduated cylinder is a plastic container that has graded markings on the side that allow you to measure volume. | #* A graduated cylinder is a plastic container that has graded markings on the side that allow you to measure volume. | ||
| Line 33: | Line 33: | ||
#Calculate the velocity of the sphere. Velocity is a measurement of distance traveled over elapsed time to travel that distance. The formula for velocity is <math>v=d/t</math> where ''v'' is velocity, ''d'' is distance traveled, and ''t'' is time. | #Calculate the velocity of the sphere. Velocity is a measurement of distance traveled over elapsed time to travel that distance. The formula for velocity is <math>v=d/t</math> where ''v'' is velocity, ''d'' is distance traveled, and ''t'' is time. | ||
#* Using your measurements, plug them into the equation <math>v=d/t</math> to find the velocity of the sphere. | #* Using your measurements, plug them into the equation <math>v=d/t</math> to find the velocity of the sphere. | ||
| − | #Calculate the viscosity of the liquid. Plug the information you have obtained into the formula for viscosity: ''viscosity = [2(p<sub>s</sub>-p<sub>l</sub>)ga<sup>2</sup>]/9v'' where ''p<sub>s</sub>'' is the density of the sphere, p<sub>l</sub> is the density of the liquid, ''g'' is acceleration due to gravity (a fixed value of 9.8 m/s<sup>2</sup>), ''a'' is the radius of the sphere, and ''v'' is the velocity of the sphere.<ref | + | #Calculate the viscosity of the liquid. Plug the information you have obtained into the formula for viscosity: ''viscosity = [2(p<sub>s</sub>-p<sub>l</sub>)ga<sup>2</sup>]/9v'' where ''p<sub>s</sub>'' is the density of the sphere, p<sub>l</sub> is the density of the liquid, ''g'' is acceleration due to gravity (a fixed value of 9.8 m/s<sup>2</sup>), ''a'' is the radius of the sphere, and ''v'' is the velocity of the sphere.<ref name="rf3" /> |
#* For example, let’s say the density of your fluid is 1.4 g/mL, the density of your sphere is 5 g/mL, the radius of the sphere is 0.002 m, and the velocity of the sphere is 0.05 m/s. | #* For example, let’s say the density of your fluid is 1.4 g/mL, the density of your sphere is 5 g/mL, the radius of the sphere is 0.002 m, and the velocity of the sphere is 0.05 m/s. | ||
#* Plugging into the equation: viscosity = [2(5 – 1.4)(9.8)(0.002)]/(9 x 0.05) = 0.314 Pa s | #* Plugging into the equation: viscosity = [2(5 – 1.4)(9.8)(0.002)]/(9 x 0.05) = 0.314 Pa s | ||
