1. The problem statement, all variables and given/known data Okay so this is probably a really easy problem, but my teacher literally doesn't teach us any thing, so can someone please help me. The coefficient of static friction between a 2.5kg box and a wooden board is .45 and the coefficient of kinetic friction between the box and the board is .28. The box is placed on the board, which is slowly lifted at one end until the box starts to slide down the board, at which point the angle theta of the board is held constant. Determine the angle theta of the board and the acceleration of the box as it slides down the board. 2. Relevant equations ok for finding theta i know I can use tan(theta)=F(x)/F(normal) for acceleration i can use a=(mass)(gravity)(sin(theta)) 3. The attempt at a solution tan(theta)=.45/F(normal) i don't know how to find the normal force.