# Determining the static and kinetic coefficients on an incline of wood on wood!

## Homework Statement

This was a lab task in which we are asked: Determine the static and dynamic coefficients of friction for a block of wood of mass 82.2grams on a plank of wood.

PART A:
To determine the static coefficient we found the angle at which point the block just started to move. This was 45.4 degrees.

For Part A, I used the equation fr = tan 45.5 degrees which gave me an answer of 1. I am not sure if this is to be expected static coefficient of a polished block of wood on a plank of wood as anything else I have read has always had a lower coefficient.

PART B:
To determine the kinetic coefficient we increased the angle to 50 degrees and timed how long the block took to cover the plank, a distance of 1 meter, when released from the top. The average time was found to be 0.69s. This is where I get stuck! I do not know how to calculate the kinetic coefficient and after much research on the net I am still as stuck as I first was... The block is accelerating but I don't know how to determine the acceleration or whether that is even necessary. Furthermore, can I just state the velocity is 0.69ms-1?
Can someone please just suggest a starting point...

## Answers and Replies

Redbelly98
Staff Emeritus
Science Advisor
Homework Helper
Try the kinematic equations, they're the ones that relate time, distance, velocity and acceleration when the acceleration is constant.