Varying fluid (density) in a cylinder rolling along an inclined plane

[mostafaelsan2005]

The time to roll down the ramp was largest for water and decreased monotonically with increasing kinematic viscosity. This is the exact opposite of the results in your original experiments. Why?

I did the experiments again, remember? I found that the results at first weren't accurate due to the lubrication of the ramp I was using. Once I did them again, and made sure that the ramp was not lubricated, I found this to be the set of values for the average time to go down the ramp. If it is needed, I can redo the experiment as I have all the equipment currently. Is the problem with the water data point?

small edit: Ill do the experiment again for all the data values, it should take me about 30 minutes or so and Ill relay the information. I'm not sure why the nearly inviscid liquid is coming out to be that with the highest time while the most viscous was the fastest. From what I understand theoretically, it should be the opposite due to less fluid resistance, right?

 

[Chestermiller]

I did the experiments again, remember? I found that the results at first weren't accurate due to the lubrication of the ramp I was using. Once I did them again, and made sure that the ramp was not lubricated, I found this to be the set of values for the average time to go down the ramp. If it is needed, I can redo the experiment as I have all the equipment currently. Is the problem with the water data point?

It is with the order of the points with respect to kinematic viscosity. Water should be the shortest time, and the time should increase monotonically with the kinematic viscosity of the fluid. In the original set of data, the time for water was only about 1.3 sec.

 

[mostafaelsan2005]

It is with the order of the points with respect to kinematic viscosity. Water should be the shortest time, and the time should increase monotonically with the kinematic viscosity of the fluid. In the original set of data, the time for water was only about 1.3 sec.

Apologies for the late response, I conducted the experiment again and I measured the times through 5 trials. Here are the average values for time:

Average time taken to reach bottom of ramp (s) ± 0.03 seconds
Water	1.33
Sunflower oil	1.35
Molasses honey	1.48
Transmission fluid	1.39

I'm not sure why there was a discrepancy in values but I have the suspicion that the timer I used in the previous set of data was damaged in some way. Here the value for water is coming out similar to the first conducted experiment so this set of data is the most accurate of the three with a functioning timer and minimal lubrication of the ramp.

 

[Chestermiller]

Apologies for the late response, I conducted the experiment again and I measured the times through 5 trials. Here are the average values for time:

Average time taken to reach bottom of ramp (s) ± 0.03 seconds
Water	1.33
Sunflower oil	1.35
Molasses honey	1.48
Transmission fluid	1.39

I'm not sure why there was a discrepancy in values but I have the suspicion that the timer I used in the previous set of data was damaged in some way. Here the value for water is coming out similar to the first conducted experiment so this set of data is the most accurate of the three with a functioning timer and minimal lubrication of the ramp.

Let’s see the graph now

 

[mostafaelsan2005]

Let’s see the graph now

The graph won't change though? The changing variable in the viscosity boundary condition parameter is the kinematic viscosity which is the same as I've said in Post #119.

 

[Chestermiller]

The graph won't change though? The changing variable in the viscosity boundary condition parameter is the kinematic viscosity which is the same as I've said in Post #119.

Of course it will. The times are different.

 

[mostafaelsan2005]

Of course it will. The times are different.

It has the same general shape but the values for t/t_0 are just different:

 

[Chestermiller]

What the hell are you talking about? This is not the same general shape at all. Now draw the two asymptotic approximations on this same graph for comparison.

 

[mostafaelsan2005]

What the hell are you talking about? This is not the same general shape at all. Now draw the two asymptotic approximations on this same graph for comparison.

The asymptotic approximations for t/t_0 will range from 1 to 1.217, correct? Otherwise it will be outside the boundary. Minimum = 1.29/1.29 and maximum = 1.57/1.29.

 

[Chestermiller]

The asymptotic approximations for t/t_0 will range from 1 to 1.217, correct? Otherwise it will be outside the boundary. Minimum = 1.29/1.29 and maximum = 1.57/1.29.

The asymptotes are y = 1.224 and $y=1+\frac{16}{15}x$, where $$y=\frac{t}{t_0}$$and $$x=\sqrt{\frac{\nu t_0}{\pi R^2}}$$

 

[Chestermiller]

The asymptotes are y = 1.224 and $y=1+\frac{16}{15}x$, where $$y=\frac{t}{t_0}$$and $$x=\sqrt{\frac{\nu t_0}{\pi R^2}}$$