Coulomb friction is the friction between_____________________?

A. 2 and V6
B. 3 and 1 kg
C. V5andV5
D. 2 and 5
E. none of the above

A. towards the wall at its upper end
B. away from the wall at its upper end
C. upwards at its upper end
D. downwards at its upper end
E. none of the above

A. bodies having relative motion
B. two dry surfaces
C. two lubricated surfaces
D. solids and liquids
E. electrically charged particles

A. toughness
B. tensile strength
C. capability of being cold worked
D. hardness
E. fatigue strength

A. coplanar
B. meet at one point ;
C. both A. and B. above
D. all be equal
E. something else

A. W
B. W sin (a + $)
C. Wtan(a + <|))
D. Wan(a-)
E. Wtana