A 3m long ladder weighing 20kg leans on a frictionless wall. Its feet rest on the floor 1m from the wall. Find the reaction forces of wall and the floor.

F_A = mg = 20 x 9.8 = 196N

Taking moments about A :

The moment due to the reaction force at wall and the weight of the ladder should be equal and opposite in direction. 

$\Rightarrow {\mathrm{F}}_{\mathrm{B}} \mathrm{x} 2\sqrt{2}=20 \mathrm{x} 9.8 \mathrm{x} \frac{1}{2}$

${\mathrm{F}}_{\mathrm{B}}=\frac{98}{2\sqrt{2}}=49 \mathrm{x} 0.7=34.3\mathrm{N}$