I have a Mathematics C assignment, with one question being about static and dynamic friction. But I think it fits this forum. Anyway, we need to conduct experiments to show if there is a difference between static and dynamic friction or not with three different surfaces. The weight of the object being tested is 0.0685kg and gravity has been assumed as -9.8m/s^2 I have calculated the coefficient of static friction for the three surfaces. This was done so by placing an object of weight 0.0685kg on a surface and increasing the angle until the object starts to slide. For wood, the average angle was 37.3°, for glass - 18.0° and for metal - 14.7°. For calculating the static coefficient of friction the weight force has been calculated as w=mg w=0.0685*-9.8 w=-0.6713 newtons This has then been subbed into 0=wsinθ-Fr 0=-0.6713*sin(37.3)-Fr Fr= 0.407 newtons 0=-wcosθ+N 0=-(-0.6713*cos(37.3))+N N=0.534 newtons μ=Fr/N μ=0.407/0.534 μ=0.762 (wood) This process has been repeated for glass (μ=0.324) and for metal (μ=0.263) Now I am completely stuck on how to calculate the coefficient of dynamic friction. I was thinking about timing how long the object takes to slide down a certain length from a set angle? But I don't know how to calculate the coefficient from that? Any ideas and help will be appreciated thanks.