I designed this lab for my physics class where we roll a hot wheels car down a length of wood that measured 1 m long. we did this process three times at varying angles and we want to investigate how changing the angle affects the coefficient of friction. The problem is, the times that we recorded end up giving us negative coefficients of friction! Whats our problem?! For example. we recorded that at 20 degrees, the car took 0.75 seconds to travel the 1 m of wood. Using the calculations we get this: 1 m = 1/2(acceleration)(0.75 seconds)^2 a = 3.56 m/s^2 coefficient of friction = (((9.8 m/s^2)(sin20))-3.56 m/s^2) / ((9.8)(cos 20)) coefficient of friction = -0.0226 help please!