Kinetic Friction--Help!?

Question

In an experiment, I got a non-zero intercept for a graph of applied force versus normal force. What could explain this?

Thanks in advance for help.

Answer 1

I assume you interpolated your data and found the intercept.
The intercept should be very small. It can arise from the variation of the coefficient of friction depending on the contact surface changes. For example, put a brick on a piece of sand paper and measure the force required to make it slip. It will vary a bit every time. This is a fundamental reason earthquakes are impossible to predict based on tension in the fault.



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