Experiment of frictional force on rolling object

  • Thread starter Illusion
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  • #1
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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

20140407_172809.jpg


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.......


expt6.jpg



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?
 
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Answers and Replies

  • #2
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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.
 
  • #3
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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?
 
  • #4
AlephZero
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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.
 

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