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.