Question

In the figure given the system is in equilibrium what is the maximum value that we can have if the friction force on the $40$ n block cannot exceed 12.0 N

Answer 1

The string fixed to support at $30$ deg having tension $T$ so horizontal component is $Tcos30$ and vertical component is Tsin30. apply equilibrium,

$Tcos30=Frictionforce\left(Fr\right)$ ----1

$Tsin30=W$ -----2

so from 1,

$Fr=12N$

we get

$T=13.85N$

From2

$W=Tsin30=13.85\times sin30=6.92N$.