Published on 19 Aug 2015

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Friction

according to the figure:

1 .If th e force p is s m all, th e body will b e

still at rest(in eq uilibrium.(

So, f<µN, N is th e nor m al reaction.

2 .After p increa s ed to reach the value of f

s=µs N, the body is on

verge of slipping or about to slide, where fs is the static frictional

force,

µs is the static frictional coefficient.

3 .When p exc e e ds f

s , the frictional force reduced to the kinetic

frictional force fk=µkN where µk is the kinetic frictional coefficient.

As a consequence the body will move.

That m e a ns:

If f < µN th e body still in e quilibrium,

If fs=µs N the body in impending motion,

If fs>µs N the body in motion.

f.8.1. If th e p = 2 0 0 n, d et er mine th e frictional force d eveloped

b etwe en th e 50-kg crate a n d the ground. The coefficient of friction

µs is 0.3.

Ans, f= 160 n

F.8.2. Det er mine the minimu m force p to prevent th e 30-kg

rod AB from sliding, the contact surface at b is s mooth, whereas