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## Homework Statement

For my Year 12 Physics EEI (Yes I have already asked for help about the actual prac, but now I'm onto writing up the theory) I conducted a prac where I rolled a fishing sinker down a 1.2m length of pipe into a tray of flour. I am now trying to use all relevant theory for the write up. I have been told (by classmates not the teacher) that as part of my theory I need to include the force of friction equation.

## Homework Equations

I can work out the Normal force, by using the eqn Fn=mg, but without knowing Fk (or Fs, but I said Fk because the sinker is rolling down the pipe, not stationary), or u (coefficient of friction, sorry I didn't use the correct symbol) how can I work out u? How can I find it with only knowing one variable?

## The Attempt at a Solution

I found the rearranged formula and it seemed simple enough: u =Fk/N, but as I said there are too many variables. I know the weight of the sinker, the lengths of the "ramp" (being the pipe) and the distance along the ground, and the angle.

How is it that I use cosine in working out in this formula? Sorry I know this is a basic question but we haven't done this work in class for about year, still no excuse though.

Any help is thoroughly appreciated