Experiment of frictional force on rolling object

[Illusion]

Recently, I have done an experiment of frictional on rolling object.

In the experiment, I have done 7 trials with different axle radii, similar to that of a yoyo on a horizontal table.

the experimental was set as this

As derived by the lab manual i received, frictional force can be plotted as a function of axle radius.

f=2mgMR(R-2r)/(3MR^2+4m(R+r)^2)

The graph plotted using my experimental data is very strange...

Both graphs are plotted by f as a function of r. The one on the right is plotted according to my experimental data. The one on the left is a plot of the equation above. Why the graphs are so different? Is there anything wrong?

 

[dauto]

It seems like you have one bad data point in your experimental graph and the plot of the function is incorrect. What were the masses m and M and what is the radius R? The function ought to change signs at r=R/2.

 

[Illusion]

It seems like you have one bad data point in your experimental graph and the plot of the function is incorrect. What were the masses m and M and what is the radius R? The function ought to change signs at r=R/2.

M = 5.743 kg

m = 50.42 g

R = 0.06355 m

i see the problem...it is a horrible and stupid mistake in changing unit...thanks for reminding


our professor reminded us that the graph is non-linear and do not have to do fitting

but the graph is fairly linear except the "bad data".

is there any other possible explanation leading to this deviation?

 

[AlephZero]

but the graph is fairly linear except the "bad data".

is there any other possible explanation leading to this deviation?

A good guess would be that the value +0.030135 should be -0.030135.

 

[paranormal]

First of all, it's great that you conducted an experiment to investigate the frictional force on a rolling object. It's an important concept in physics and understanding it can have practical applications in many areas.

Now, to address your question about the difference between your experimental data and the theoretical equation, there could be several factors at play. One possibility is that there may have been errors in your experimental setup or data collection. It's important to carefully control all variables and take accurate measurements in any scientific experiment.

Another possibility is that there may be limitations or simplifications in the theoretical equation you used. The equation you provided assumes a perfectly circular object and a constant coefficient of friction, which may not be the case in your experimental setup. Additionally, there may be other factors such as air resistance or imperfections in the surface of the table that could affect the results.

It's also important to note that in science, it's common to see discrepancies between theoretical predictions and experimental data. This is why it's important to conduct multiple trials and compare your results to the expected trends.

In order to further investigate the differences between your experimental data and the theoretical equation, you could try to identify and control for any sources of error in your experiment. You could also try to expand your experiment to include different variables, such as varying the surface of the table or using different objects with different shapes.

Overall, it's important to remember that science is a continuous process of learning and refining our understanding. Your experiment and its results are an important step in that process, and it's always valuable to question and explore any discrepancies or unexpected results.