What are concurrent forces ?

Explanation

Concurrent forces : if line of action of all given forces passes through same point then these forces are called concurrent forces
If only force `vec(f ) ` act on a particle then it has accelerated motion . It cannot remain in equilibrium.
If force `vec(F)_(1)` and `vec(F)_(2)` act on particle then for equilibrium `Sigma vec(F)` = means
this condition is shown figure

If there force `vec(F)_(1) vec(F)_(2)` and `vec(F)_(3)` act on a particle then for equilibrium `Sigma vec(F ) = 0`
`:. vec(F)_(3) = - (vec(F)_(1)+ vec(F)_(2))`
This is represented in diagram shown below

by parallelogram law of force resultant force of `vec(F)_(1) ` and `vec(F)_(2)` is prepresented by diagonal when force `vec(F)_(3)` equal to same magnitude is applied in opposite direction particle will be in equilibrium
By triangle of vector
`vec(PQ) + vec(QR) = vec(RP) = 0`
`:. Sigma vec(F ) = 0`
if `vec(F)_(1) + vec(F)_(2) ` and `vec(F)_(3)` make angle with coordinate axis then for equilibrium
`vec(F )_(1y) + vec(F)_(2y) + vec(F )_(3y) = 0`
`vec(F)_(1 z) + vec (f )_(1x ) + vec( F)_(3z) = 0`
where `vec(F)_(1x) , vec(F )_(1y) , vec(F )_(1z)` are respective component with x , y and axis respectively.