The force P is applied to the $57-$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$=157$N$,$ and $($c$)$P$=233$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 $\backslash$mu $\_($s$)=0\mathrm{.}15$ and $\backslash$mu $\_($k$)=0\mathrm{.}10,$ respectively. The friction force is

positive if up the incline, negative if down the incline.

Answers:

$($a$)$ F$=$

N

$($b$)$ F$=$

N

$($c$)$ F$=$

$5$

N

$($d$)$ P$=$

$5$

N