# How to determine the force of friction from a graph?

TSny
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Note that when we write Fapplied - Ffriction = ma, then the symbol Ffriction represents the magnitude of the force of friction. That is, Ffriction represents a positive number. We take into account the negative direction of the friction force with the minus sign in Fapplied - Ffriction.

And to calculate percentage error I would do: (1.2729 - 1.5758)/ 1.5758, or ((slope experimental - slope theoretical)/ slope theoretical) without considering the force of friction?

Thank you for all the help.

TSny
Homework Helper
Gold Member
Right. You should note that friction does not affect the slope of the graph, only the y-intercept.