How can I calculate the friction provided by a piece of wood ( needed to calculate acceleration accurately)?

Question

I put a car on top of a ramp, I assumed that the acceleration would be constant but I forgot about the friction from the wood, I used a=g Sin x but now thats wrong because I need to get the friction of the wood.

Answer 1

What is the function here? Keep in mind that resistance from friction will be a constant if the ramp has a constant angle. Acceleration will be less because the acting force is less, but will still be constant.

For friction of wood, try searching for it. Could also consult the appendix of your physics or an engineering book.