The force P is applied to the 40-kg block when it is at rest. Determine the magnitude and direction of the friction force exerted by the surface on the block if (a) P= 0, (b) P= 158 N, and (c) P= 241 N. (d) What value of P is required to initiate motion up the incline? The static and kinetic coefficients of friction between the block and the incline are /; = 0.25 and //k = 0.21, respectively. The friction force is positive if up the incline, negative if down the incline. 40 kg 22- 4. = 0.25 MR = 0.21 16' Answers: (a) F = i N (b) F = i N (c) F = i N (d) P = i N