A unifrom pole of mass 20kg and length 6m is supported horizontally at its ends by two knife edges A and B. A mass of 120kg is now suspended at a distance 2m from A. Calculate reaction forces at the knife edges.

Explanation

Given W=20 kg wt, P=120 kgwt, AC=BC=3m, AD=2m
For Static equilibrium sum of upward forces = sum of downward forces
`R_1+R_2=120+20=140kg wt`
Taking moments about B, we write
`20bar(BC)+120bar(BD)=R_1bar(BA)`, Moment of `R_2` about `B=O`
`20xx3+120(4)=R_1(6)`
`R_1=(540)/6=90kg wt`
and `R_2=140-90=50kg wt`