Applying Newton's Second Law and the equation for static friction (F = u, N), we can prove that the coefficient of static friction ( ) is related to the minimum angle, 0, that causes the block to slip (see Figure 5) by the equation u = tan(0). Starting with the knowledge that the total force on an object is the force acting in one direction, minus the force of friction which opposes it: F_ = F acceleration - F friction solve for this relationship - u. = tan(0). Hint: Break this down into the x and y components of force and remember the trigonometric identity tan (0 )= sin (0) cos (0 )