Density from a viscosity experiment

Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
4 replies · 1K views
archaic
Messages
688
Reaction score
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?
 
Physics news on Phys.org
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.
 
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.
 
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
 
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.