A thin plank of mass m and length l is pivoted at one end and it is held stationary in horizontal position by means of a light thread as shown in the figure then find out the force on the pivot.

Explanation

Free body diagram of the plank is shown in figure.
` :.` plank is in equilibrium condition
So `F_("net") & tau _("net")` on the plank is zero
(i) from `F_("net") = 0 `
`rArr F_("net x") = 0 `
`N_(1) = 0 `
Now ` F_("net y")= 0 `
`rArr N_(2) + T = mg " " . . . (i)`
from `tau_("net") = 0 `
`rArr tau_("net")` about point A is zero
So `N_(2)*l = mg . l//2`
`rArr N_(2) = (mg)/(2)`