Density from a viscosity experiment

In summary, the conversation discusses an experiment involving a small ball being dropped in a viscous liquid to measure its falling time. The equation used in the experiment is given, and the question is posed about finding a relation between diameter and time to determine the density of the ball. It is unclear if all necessary information is provided for this task, leading to confusion and a potential resolution with the professor.
  • #1
archaic
688
214
Homework Statement
Identify the relation between the Diameter and the time to plot a graph to determine
the density of the pellet. Would you get a linear equation? If not, linearize the
equation.
Relevant Equations
$$v_t=\frac{(\rho_b-\rho_l)g}{18\eta}D^2$$
The body is a small ball. The experiment consists in dropping this ball, while varying the diameter each 3 trials, in a viscous liquid and measuring its falling time: ##D_i\sim t_1,\,t_2,\,t_3##.

The equation we are using is:
$$\frac{\Delta x}{\Delta t}\approx\frac{(\rho_b-\rho_l)g}{18\eta}D^2$$
I am asked to figure out a relation between the time and the diameter and find the density of the ball (I will be using Excel), but everything is unknown; falling distance, ##\eta##, ##\rho_l##.

Is this possible? If yes, can you please hint me to something?
 
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  • #2
archaic said:
Homework Statement:: Identify the relation between the Diameter and the time to plot a graph to determine
the density of the pellet. Would you get a linear equation? If not, linearize the
equation.
Relevant Equations:: $$v_t=\frac{(\rho_b-\rho_l)g}{18\eta}D^2$$

The body is a small ball. The experiment consists in dropping this ball, while varying the diameter each 3 trials, in a viscous liquid and measuring its falling time: ##D_i\sim t_1,\,t_2,\,t_3##.

The equation we are using is:
$$\frac{\Delta x}{\Delta t}\approx\frac{(\rho_b-\rho_l)g}{18\eta}D^2$$
I am asked to figure out a relation between the time and the diameter and find the density of the ball (I will be using Excel), but everything is unknown; falling distance, ##\eta##, ##\rho_l##.

Is this possible? If yes, can you please hint me to something?
If you have stated the question exactly as given to you, I would say it is asking for the procedure by which you would determine the density of the pellet if you had all that information.
 
  • #3
haruspex said:
If you have stated the question exactly as given to you, I would say it is asking for the procedure by which you would determine the density of the pellet if you had all that information.
No, I am actually supposed to get a numerical value at the end. I think that I will email the professor.
 
  • #4
haruspex said:
If you have stated the question exactly as given to you, I would say it is asking for the procedure by which you would determine the density of the pellet if you had all that information.
It turns out that the professor wanted to see who would really work on the problem. o_O
 
  • #5
archaic said:
It turns out that the professor wanted to see who would really work on the problem. o_O
Sounds like a rationalisation after she/he realized the oversight.
 

What is the purpose of a viscosity experiment?

A viscosity experiment is used to measure the resistance of a fluid to flow. This can provide information about the density and composition of the fluid.

How is density calculated from a viscosity experiment?

Density can be calculated from a viscosity experiment by using the formula density = mass / volume. The mass of the fluid can be measured and the volume can be calculated by measuring the time it takes for a known volume of the fluid to flow through a narrow tube.

What factors can affect the accuracy of density measurements from a viscosity experiment?

The accuracy of density measurements from a viscosity experiment can be affected by factors such as temperature, pressure, and the type of fluid being tested. It is important to control these variables in order to obtain accurate results.

How does the density of a fluid affect its viscosity?

Generally, the higher the density of a fluid, the higher its viscosity will be. This is because denser fluids have more molecules and therefore more resistance to flow. However, other factors such as temperature and pressure can also affect viscosity.

Can density be used to identify a substance in a viscosity experiment?

Yes, density can be used to identify a substance in a viscosity experiment. Each substance has a unique density, so by measuring the density of a fluid, it can be compared to known values to determine its identity.

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