1. The problem statement, all variables and given/known data A brick is on a 121 cm plank, and the plank is lifted gradually until the brick begins to slide, when the plank is lifted 48cm in the air at an angle of 30º. I need to find the Frictional Force, and µ kinetic. How do I find these things knowing only these three things? 2. Relevant equations Ff=(µk)(Fn) let Fn= Normal Force F=ma g=9.81 m/s/s Fn=mg(Cosø) 3. The attempt at a solution I tried using the first equation I mentioned, but was unable to figure how to get both values. Help is much appreciated.