1. READING QUIZ The friction that exist between two contacting surfaces in the absence of lubrication is called _________. A) fluid friction B) normal friction C) Newton's friction D) dry or Coulomb friction

2. READING QUIZ What should the minimum coefficient of static friction be to prevent slipping of the block. A)  s = sin –1 (  ) B)  s = cos -1 (  ) C)  s = tan -1 (  ) D)  s = cot -1 (  ) W 

3. CONCEPT QUIZ Select the false statement from the following. A) The maximum static friction force that can be developed is independent of the area of contact. B) The friction force existing between two moving bodies is the kinetic friction force. C) The coefficient of static friction is smaller than the coefficient of kinetic friction. D) At the point of impeding motion, the friction force reaches its maximum value

4. CONCEPT QUIZ What is the minimum force P necessary to create an impending motion condition for pushing the 100 lb block up the incline? A) 92 lb B) 32 lb C) 60 lb D) 104 lb W= 100 lb P 4 3  s = 0.4

5. ATTENTION QUIZ The friction force acts _______ to the contacting surfaces and in the ________ direction of the relative motion. A) perpendicular, opposite B) tangent, opposite C) perpendicular, same D) tangent, same

6. ATTENTION QUIZ In the free body diagram shown, force P is just large enough to impend motion. Select the distance x locating where the normal force acts? A) 0.8 ´´ B) 1.0 ´´ C) 3 ´´ D) 4 ´´ W=100lb G 4´´ 6´´ x N  s = 0.25 F s =  s N P