# Finding the coefficient of viscosity

• joshm12
In summary, to calculate the viscosity, we need to find the slope of the line using the change in y/change in x and then use this value in the given equation. The measurements for this problem were given and it is unclear if a plot was made to justify the use of the slope. It is also mentioned that the data does not exclude static friction and a different approach may be equally justified.
joshm12
Homework Statement
How do I work out the coefficient of viscosity when the slope of a graph =0.34
n= coefficient of viscosity
v=speed of rotation
f= force required to maintain speed
Relevant Equations
F=1.67nv
"Calculate the gradient (or slope) of the line and use this and the equation above to calculate the value for the viscosity, η. You MUST use the gradient to calculate the viscosity." here are the results:

I'm not sure if it's just me who finds this confusing

Hello @joshm12, !

What did you find for the slope of the line ? And how did you do that ? By forcing an intercept 0 ?
Did you make a plot to see if that is justified ?

Are these your own measurements or were they given as part of the problem statement ?

@BvU I used the change in y/change in x to find the slope of the line and got 0.34. and the measurements were given as part of the problem

Last edited:
joshm12 said:
I used the change in y/change in x
Yes, I know that. How did you do it ?

This is for flow between a rotating cylinder and a stationary cylinder. Is the gap between the cylinders small?

BvU said:
What did you find for the slope of the line ? And how did you do that ? By forcing an intercept 0 ?
Did you make a plot to see if that is justified ?

I think @joshm12 didn't bother: he wasn't seen after #3.

The data don't exclude static friction, so ax+b seems equally justified and gives a slope 0.3

## 1. What is the coefficient of viscosity?

The coefficient of viscosity, also known as dynamic viscosity, is a measure of a fluid's resistance to flow. It is a physical property that describes how easily a fluid can be deformed by a shear stress.

## 2. How is the coefficient of viscosity measured?

The coefficient of viscosity can be measured using various techniques, such as viscometry, rheometry, and capillary tube methods. These methods involve applying a known force or stress to the fluid and measuring the resulting deformation or flow rate.

## 3. What factors affect the coefficient of viscosity?

The coefficient of viscosity is affected by several factors, including temperature, pressure, and the type of fluid. Generally, as temperature increases, the coefficient of viscosity decreases, while an increase in pressure can cause an increase in viscosity. The type of fluid also plays a significant role, as different fluids have different molecular structures that affect their viscosity.

## 4. Why is the coefficient of viscosity important?

The coefficient of viscosity is an essential property in fluid dynamics and is used in various applications, such as designing pipelines, calculating frictional losses in flow, and understanding the behavior of fluids in different environments. It is also crucial in industries such as food processing, pharmaceuticals, and petroleum, where precise control of fluid flow is necessary.

## 5. How do different fluids have different coefficients of viscosity?

The molecular structure of a fluid determines its coefficient of viscosity. For example, fluids with longer, more complex molecules, such as oils, tend to have higher viscosities compared to fluids with shorter, simpler molecules, such as water. Additionally, the strength of intermolecular forces also plays a role in determining the coefficient of viscosity.

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