Fluids mechanics homework, feel like I have messed up the equations

In summary, equation 3 has a typo where the dynamic viscosity (μ) is included in the denominator, this causes the equation to be incorrect. To solve for the coefficient of viscosity, you must use the values found in the first table (s, p, and u) and the second table (g, Ps, and P1). The last picture shows how to solve for the coefficient of viscosity using these values.
  • #1
Meckii
3
0
Homework Statement
Confused with trying to find the values in the equation although I feel like im just messing up the equation in my head.
Relevant Equations
Equation 3: Coefficient of viscosity = 4 x pi x r^3 × g / 3 x 6 x pi x coefficient of visc x mean velocity of ball
(Ps - P1) = (2/9) x r^2 x g ((ps - p1) / u)

Equation 5: v = dynamic viscosity / density
Edit: So I have written out equation 3 again and taken a picture to show my working out, the 2 things that I am confused about is how do I find the coefficient of viscosity? I know that syrup is high viscosity and water is low viscosity but I don't know the equation to get the actual value. The 2nd issue I have is when I have the coefficient of viscosity value, do I just use the 1st part of equation 3 to find the Dynamic Viscosity or do I have to somehow combine both sides of the equation? If it is the latter I do not have a clue how to work out both together. The last 2 images are what I have worked out just.

I have attempted my solution on the images attached, the first 3 images show the equations needed for the questions while the last 4 or 5 images show my working out and the way I tried attempting the questions.

The 4th pic shows the practical work done showing the specific gravity, s and the Density, p. While the 6th page shows my attempt at the equation 3 and equation 5, the final page shows equation 5 questions at the top also. While in the 5th pic the times that the ball took to travel a certain distance is shown at the top.

All I really ask is a little bit of guidance as it has stumped me quite a bit and I am unsure how to progress with the correct values/answers.

Values achieved,
s = shown in the first table
Density, p = shown in the 2nd table
u = mean average is shown in last pic
g = 9.81
Ps = 7.850 (I am assuming this is correct, density of steel which I looked up)
P1 = given in the density table on page 4, all 4 values
r = the radius which is known as 1.59mm, 2.38mm and 3.175mm
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Last edited:
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  • #3
Lnewqban said:
Equation #3 has a typo, as it incorrectly includes the dynamic viscosity (μ) in the denominator.
Please, see:
https://en.m.wikipedia.org/wiki/Stokes'_law

Welcome, Meckii :cool:
Lnewqban said:
Equation #3 has a typo, as it incorrectly includes the dynamic viscosity (μ) in the denominator.
Please, see:
https://en.m.wikipedia.org/wiki/Stokes'_law

Welcome, Meckii :cool:
Updated, surprised i missed that, thanks for letting me know though, ended up forgetting to add the pics also
 
  • #4
Edit: I pictures 4-6 are the first pictures added, pictures 7-8 are the new pictures I have added which I just wrote out.
 

What is fluid mechanics?

Fluid mechanics is the branch of physics that deals with the study of fluids and the forces that act on them. It involves the study of how fluids move, behave, and interact with their surroundings.

What are some common equations used in fluid mechanics?

Some common equations used in fluid mechanics include the Navier-Stokes equations, Bernoulli's equation, and the continuity equation. These equations help to describe the behavior of fluids under different conditions.

What should I do if I have made a mistake in my fluid mechanics homework?

If you have made a mistake in your fluid mechanics homework, the first step is to carefully review your work and identify where the mistake was made. Then, try to understand why the mistake was made and correct it. If you are still unsure, it is always helpful to seek guidance from a teacher or tutor.

What are some common mistakes made in fluid mechanics homework?

Some common mistakes made in fluid mechanics homework include incorrect use of equations, incorrect units, and incorrect assumptions about the behavior of fluids. It is important to carefully check your work and double-check your calculations to avoid these mistakes.

How can I improve my understanding of fluid mechanics?

To improve your understanding of fluid mechanics, it is important to practice solving problems and to seek help when needed. It can also be helpful to visualize the behavior of fluids and to make connections between theory and real-world applications. Additionally, staying up-to-date on current research and developments in the field can also deepen your understanding.

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