2.1 INTRODUCTION R N G Force of friction f W f W P Direction of impending motion N Fig. 2.1 2.1.1 Engineering Applications of Friction ­ f Impending motion Static fricton fm Dynamic friction P It is the angle made by the resultant () of the normal reaction () and limiting force of friction ( ) and made with the direction of normal reaction. is the resultant of normal reaction and force of friction . = 2 2 is the angle of friction tan = or = tan 1 N R P f W It is ratio of limiting frictional force and the normal reaction. The coefficient of friction, = = tan = N f = N Y X W cos Motion W sin W ­ ­ ­ ­ 20 N N P sin 25° 25° f W ­ ­ ­ ­ ­ ­ N P P sin P cos f W ­­ n N si N f N cos Y X W P N Y X W cos f W sin W s N P co Y P sin X P W cos f W sin W P P sin Y N P cos X W cos f W sin W P f N Y X W cos W sin W P Y N X W cos f W sin W ­ ­­ P N Y X W cos f W sin W ­ s co N P in Ps Y P X W cos f W sin W ­ 5m 0.2 RR fR X RF fF mg cos mg sin W = mg m 0.5 0.5 m Y ­ ­ ­ fB B B L/2 L W fA A O RA RB ­­­ B RB 300 N fA A 60° RA ­ ­ B RB 10 m 5m 6m 20 N fA A RA O 8m ­ fB B RB l x 1.5W W l/2 fA 45° A O RA ­ ­ B RB 3.5 m 3m 7m 800 N 600 N fA 60° A O RA ­ ­ ­ ­ ­ ­ ­ ­ Y R1 f1 N1 W X R2 N2 R2 cos ( + ) f2 R2 sin ( + ) R2 sin ( + ) f2 Y R2 cos ( + ) R2 N2 P X R3 N3 Motion f3 ­ ­ ­ ­ Driver Slack side Follower T2 r2 r1 Tight side T1 ­ ­ ­­ ­ ­ d r T1 T2 ­ ­ ­ ­ ­ ­ 0.9155 N-m Ans. Example 2.14: ­ Solution: 25 kW Ans. Example 2.15: Solution: 1.054 kN.m Ans. Example 2.17: ­ ­ ­ 0.5 m T2 T1 Solution: 1562.2 N Ans. Example 2.18: ­ ­ ­ ­ ­ ­ ­ ­ R W P p dm ­ ­ ­ ­ ­ ­
