Is the Kinetic Friction Coefficient Consistent Across Different Modes of Motion?

[badsis]

Hello,

Here is my question:
should the kinetic friction coefficient Fk be the same when the object with mass m is pulled with a constant velocity as the kinetic friction coefficient with the same mass m when it was pushed and released.
The measurements in the second case were taken from the decelerating part of the Force vs. Time graph.

I have several table with data many of which i have calculated myself.
from the formula: Fk = ;mu * Fn
Fk - kinetik friction force,
;mu - coefficient of friction kinetic force
Fn - normal force
in the first case I have:
m = 0.09 kg
Fk = 0.1387 N (the uncertainty here is 17% ! Fk = 0.1387 +- 0.0238)
Fn = 0.882 N
=> ;mu = 0.1573

In the second case:
m = 0.09 kg
Fk = 0.2585 N
Fn = 0.882 N
=> ;mu = 0.2931
here i also have uncertainty in acceleration which I use in order to find Fk.

So, my question is: Should the coefficient ;mu be different in two cases or do I have such a big error?

THANKS!

 

[Kurdt]

The coefficient should be the same. If you are pulling the mass be careful that no component of the force acts upwards since this will reduce the normal force.

 

[Moetasim]

Hello,

Thank you for your question regarding friction coefficients. The kinetic friction coefficient (Fk) should theoretically be the same in both cases, regardless of whether the object is pulled with a constant velocity or pushed and released. This is because the coefficient of kinetic friction is a measure of the amount of force needed to maintain a constant velocity, and it is independent of the direction of motion. However, in practice, there may be slight variations due to experimental error or other factors.

Based on the data you have provided, it appears that there may be a difference in the measured values of Fk and ;mu. This could be due to several reasons, such as inconsistencies in the experimental setup or limitations of the equipment used for measurements. It is also important to note that the uncertainty in the measurements may contribute to the difference in the calculated values of ;mu.

In order to accurately determine the coefficient of kinetic friction, it is important to repeat the experiment multiple times and take into account any sources of error. This will help to reduce the uncertainty in the measurements and provide a more accurate value for ;mu. I recommend consulting with your lab instructor or a colleague to troubleshoot any potential sources of error in your experiment and to discuss ways to improve the accuracy of your measurements.

Overall, it is expected that the kinetic friction coefficient should be consistent in both cases, but slight variations may occur in practice. It is important to carefully analyze your data and consider sources of error in order to accurately determine the coefficient of kinetic friction. I hope this helps to answer your question. Good luck with your experiments!